{ } CodeMirror

/* User manual and
   reference guide */


CodeMirror is a code-editor component that can be embedded in Web pages. The core library provides only the editor component, no accompanying buttons, auto-completion, or other IDE functionality. It does provide a rich API on top of which such functionality can be straightforwardly implemented. See the add-ons included in the distribution, and the CodeMirror UI project, for reusable implementations of extra features.

CodeMirror works with language-specific modes. Modes are JavaScript programs that help color (and optionally indent) text written in a given language. The distribution comes with a number of modes (see the mode/ directory), and it isn't hard to write new ones for other languages.

Basic Usage

The easiest way to use CodeMirror is to simply load the script and style sheet found under lib/ in the distribution, plus a mode script from one of the mode/ directories. (See the compression helper for an easy way to combine scripts.) For example:

<script src="lib/codemirror.js"></script>
<link rel="stylesheet" href="../lib/codemirror.css">
<script src="mode/javascript/javascript.js"></script>

Having done this, an editor instance can be created like this:

var myCodeMirror = CodeMirror(document.body);

The editor will be appended to the document body, will start empty, and will use the mode that we loaded. To have more control over the new editor, a configuration object can be passed to CodeMirror as a second argument:

var myCodeMirror = CodeMirror(document.body, {
  value: "function myScript(){return 100;}\n",
  mode:  "javascript"

This will initialize the editor with a piece of code already in it, and explicitly tell it to use the JavaScript mode (which is useful when multiple modes are loaded). See below for a full discussion of the configuration options that CodeMirror accepts.

In cases where you don't want to append the editor to an element, and need more control over the way it is inserted, the first argument to the CodeMirror function can also be a function that, when given a DOM element, inserts it into the document somewhere. This could be used to, for example, replace a textarea with a real editor:

var myCodeMirror = CodeMirror(function(elt) {
  myTextArea.parentNode.replaceChild(elt, myTextArea);
}, {value: myTextArea.value});

However, for this use case, which is a common way to use CodeMirror, the library provides a much more powerful shortcut:

var myCodeMirror = CodeMirror.fromTextArea(myTextArea);

This will, among other things, ensure that the textarea's value is updated with the editor's contents when the form (if it is part of a form) is submitted. See the API reference for a full description of this method.


Both the CodeMirror function and its fromTextArea method take as second (optional) argument an object containing configuration options. Any option not supplied like this will be taken from CodeMirror.defaults, an object containing the default options. You can update this object to change the defaults on your page.

Options are not checked in any way, so setting bogus option values is bound to lead to odd errors.

These are the supported options:

value (string or Doc)
The starting value of the editor. Can be a string, or a document object.
mode (string or object)
The mode to use. When not given, this will default to the first mode that was loaded. It may be a string, which either simply names the mode or is a MIME type associated with the mode. Alternatively, it may be an object containing configuration options for the mode, with a name property that names the mode (for example {name: "javascript", json: true}). The demo pages for each mode contain information about what configuration parameters the mode supports. You can ask CodeMirror which modes and MIME types have been defined by inspecting the CodeMirror.modes and CodeMirror.mimeModes objects. The first maps mode names to their constructors, and the second maps MIME types to mode specs.
theme (string)
The theme to style the editor with. You must make sure the CSS file defining the corresponding .cm-s-[name] styles is loaded (see the theme directory in the distribution). The default is "default", for which colors are included in codemirror.css. It is possible to use multiple theming classes at once—for example "foo bar" will assign both the cm-s-foo and the cm-s-bar classes to the editor.
indentUnit (integer)
How many spaces a block (whatever that means in the edited language) should be indented. The default is 2.
smartIndent (boolean)
Whether to use the context-sensitive indentation that the mode provides (or just indent the same as the line before). Defaults to true.
tabSize (integer)
The width of a tab character. Defaults to 4.
indentWithTabs (boolean)
Whether, when indenting, the first N*tabSize spaces should be replaced by N tabs. Default is false.
electricChars (boolean)
Configures whether the editor should re-indent the current line when a character is typed that might change its proper indentation (only works if the mode supports indentation). Default is true.
rtlMoveVisually (boolean)
Determines whether horizontal cursor movement through right-to-left (Arabic, Hebrew) text is visual (pressing the left arrow moves the cursor left) or logical (pressing the left arrow moves to the next lower index in the string, which is visually right in right-to-left text). The default is false on Windows, and true on other platforms.
keyMap (string)
Configures the keymap to use. The default is "default", which is the only keymap defined in codemirror.js itself. Extra keymaps are found in the keymap directory. See the section on keymaps for more information.
extraKeys (object)
Can be used to specify extra keybindings for the editor, alongside the ones defined by keyMap. Should be either null, or a valid keymap value.
lineWrapping (boolean)
Whether CodeMirror should scroll or wrap for long lines. Defaults to false (scroll).
lineNumbers (boolean)
Whether to show line numbers to the left of the editor.
firstLineNumber (integer)
At which number to start counting lines. Default is 1.
lineNumberFormatter (function)
A function used to format line numbers. The function is passed the line number, and should return a string that will be shown in the gutter.
gutters (array)
Can be used to add extra gutters (beyond or instead of the line number gutter). Should be an array of CSS class names, each of which defines a width (and optionally a background), and which will be used to draw the background of the gutters. May include the CodeMirror-linenumbers class, in order to explicitly set the position of the line number gutter (it will default to be to the right of all other gutters). These class names are the keys passed to setGutterMarker.
fixedGutter (boolean)
Determines whether the gutter scrolls along with the content horizontally (false) or whether it stays fixed during horizontal scrolling (true, the default).
readOnly (boolean)
This disables editing of the editor content by the user. If the special value "nocursor" is given (instead of simply true), focusing of the editor is also disallowed.
showCursorWhenSelecting (boolean)
Whether the cursor should be drawn when a selection is active. Defaults to false.
undoDepth (integer)
The maximum number of undo levels that the editor stores. Defaults to 40.
tabindex (integer)
The tab index to assign to the editor. If not given, no tab index will be assigned.
autofocus (boolean)
Can be used to make CodeMirror focus itself on initialization. Defaults to off. When fromTextArea is used, and no explicit value is given for this option, it will be set to true when either the source textarea is focused, or it has an autofocus attribute and no other element is focused.

Below this a few more specialized, low-level options are listed. These are only useful in very specific situations, you might want to skip them the first time you read this manual.

dragDrop (boolean)
Controls whether drag-and-drop is enabled. On by default.
onDragEvent (function)
When given, this will be called when the editor is handling a dragenter, dragover, or drop event. It will be passed the editor instance and the event object as arguments. The callback can choose to handle the event itself, in which case it should return true to indicate that CodeMirror should not do anything further.
onKeyEvent (function)
This provides a rather low-level hook into CodeMirror's key handling. If provided, this function will be called on every keydown, keyup, and keypress event that CodeMirror captures. It will be passed two arguments, the editor instance and the key event. This key event is pretty much the raw key event, except that a stop() method is always added to it. You could feed it to, for example, jQuery.Event to further normalize it.
This function can inspect the key event, and handle it if it wants to. It may return true to tell CodeMirror to ignore the event. Be wary that, on some browsers, stopping a keydown does not stop the keypress from firing, whereas on others it does. If you respond to an event, you should probably inspect its type property and only do something when it is keydown (or keypress for actions that need character data).
cursorBlinkRate (number)
Half-period in milliseconds used for cursor blinking. The default blink rate is 530ms.
cursorHeight (number)
Determines the height of the cursor. Default is 1, meaning it spans the whole height of the line. For some fonts (and by some tastes) a smaller height (for example 0.85), which causes the cursor to not reach all the way to the bottom of the line, looks better
workTime, workDelay (number)
Highlighting is done by a pseudo background-thread that will work for workTime milliseconds, and then use timeout to sleep for workDelay milliseconds. The defaults are 200 and 300, you can change these options to make the highlighting more or less aggressive.
pollInterval (number)
Indicates how quickly CodeMirror should poll its input textarea for changes (when focused). Most input is captured by events, but some things, like IME input on some browsers, don't generate events that allow CodeMirror to properly detect it. Thus, it polls. Default is 100 milliseconds.
flattenSpans (boolean)
By default, CodeMirror will combine adjacent tokens into a single span if they have the same class. This will result in a simpler DOM tree, and thus perform better. With some kinds of styling (such as rounded corners), this will change the way the document looks. You can set this option to false to disable this behavior.
viewportMargin (integer)
Specifies the amount of lines that are rendered above and below the part of the document that's currently scrolled into view. This affects the amount of updates needed when scrolling, and the amount of work that such an update does. You should usually leave it at its default, 10. Can be set to Infinity to make sure the whole document is always rendered, and thus the browser's text search works on it. This will have bad effects on performance of big documents.


A CodeMirror instance emits a number of events, which allow client code to react to various situations. These are registered with the on method (and removed with the off method). These are the events that fire on the instance object. The name of the event is followed by the arguments that will be passed to the handler. The instance argument always refers to the editor instance.

"change" (instance, changeObj)
Fires every time the content of the editor is changed. The changeObj is a {from, to, text, next} object containing information about the changes that occurred as second argument. from and to are the positions (in the pre-change coordinate system) where the change started and ended (for example, it might be {ch:0, line:18} if the position is at the beginning of line #19). text is an array of strings representing the text that replaced the changed range (split by line). If multiple changes happened during a single operation, the object will have a next property pointing to another change object (which may point to another, etc).
"beforeChange" (instance, change)
This event is fired before a change is applied, and its handler may choose to modify or cancel the change. The change object has from, to, and text properties, as with the "change" event, but never a next property, since this is fired for each individual change, and not batched per operation. It also has update(from, to, text) and cancel() methods, which may be used to modify or cancel the change. All three arguments to update are optional, and can be left off to leave the existing value for that field intact. Note: you may not do anything from a "beforeChange" handler that would cause changes to the document or its visualization. Doing so will, since this handler is called directly from the bowels of the CodeMirror implementation, probably cause the editor to become corrupted.
"cursorActivity" (instance)
Will be fired when the cursor or selection moves, or any change is made to the editor content.
"beforeSelectionChange" (instance, selection)
This event is fired before the selection is moved. Its handler may modify the resulting selection head and anchor. The selection parameter is an object with head and anchor properties holding {line, ch} objects, which the handler can read and update. Handlers for this event have the same restriction as "beforeChange" handlers — they should not do anything to directly update the state of the editor.
"viewportChange" (instance, from, to)
Fires whenever the view port of the editor changes (due to scrolling, editing, or any other factor). The from and to arguments give the new start and end of the viewport.
"gutterClick" (instance, line, gutter, clickEvent)
Fires when the editor gutter (the line-number area) is clicked. Will pass the editor instance as first argument, the (zero-based) number of the line that was clicked as second argument, the CSS class of the gutter that was clicked as third argument, and the raw mousedown event object as fourth argument.
"focus", "blur" (instance)
These fire whenever the editor is focused or unfocused.
"scroll" (instance)
Fires when the editor is scrolled.
"update" (instance)
Will be fired whenever CodeMirror updates its DOM display.

It is also possible to register events on other objects. Use CodeMirror.on(handle, "eventName", func) to register handlers on objects that don't have their own on method. Document objects (instances of CodeMirror.Doc) emit the following events:

"change" (doc, changeObj)
Fired whenever a change occurs to the document. changeObj has a similar type as the object passed to the editor's "change" event, but it never has a next property, because document change events are not batched (whereas editor change events are).
"beforeChange" (doc, change)
See the description of the same event on editor instances.
"cursorActivity" (doc)
Fired whenever the cursor or selection in this document changes.
"beforeSelectionChange" (doc, selection)
Equivalent to the event by the same name as fired on editor instances.

Line handles (as returned by, for example, getLineHandle) support these events:

"delete" ()
Will be fired when the line object is deleted. A line object is associated with the start of the line. Mostly useful when you need to find out when your gutter markers on a given line are removed.
"change" ()
Fires when the line's text content is changed in any way (but the line is not deleted outright).

Marked range handles, as returned by markText and setBookmark, emit the following events:

"clear" ()
Fired when the range is cleared, either through cursor movement in combination with clearOnEnter or through a call to its clear() method. Will only be fired once per handle. Note that deleting the range through text editing does not fire this event, because an undo action might bring the range back into existence.
"hide" ()
Fired when the last part of the marker is removed from the document by editing operations.
"unhide" ()
Fired when, after the marker was removed by editing, a undo operation brought the marker back.

Line widgets, returned by addLineWidget, fire these events:

"redraw" ()
Fired whenever the editor re-adds the widget to the DOM. This will happen once right after the widget is added (if it is scrolled into view), and then again whenever it is scrolled out of view and back in again, or when changes to the editor options or the line the widget is on require the widget to be redrawn.


Keymaps are ways to associate keys with functionality. A keymap is an object mapping strings that identify the keys to functions that implement their functionality.

Keys are identified either by name or by character. The CodeMirror.keyNames object defines names for common keys and associates them with their key codes. Examples of names defined here are Enter, F5, and Q. These can be prefixed with Shift-, Cmd-, Ctrl-, and Alt- (in that order!) to specify a modifier. So for example, Shift-Ctrl-Space would be a valid key identifier.

Alternatively, a character can be specified directly by surrounding it in single quotes, for example '$' or 'q'. Due to limitations in the way browsers fire key events, these may not be prefixed with modifiers.

The CodeMirror.keyMap object associates keymaps with names. User code and keymap definitions can assign extra properties to this object. Anywhere where a keymap is expected, a string can be given, which will be looked up in this object. It also contains the "default" keymap holding the default bindings.

The values of properties in keymaps can be either functions of a single argument (the CodeMirror instance), strings, or false. Such strings refer to properties of the CodeMirror.commands object, which defines a number of common commands that are used by the default keybindings, and maps them to functions. If the property is set to false, CodeMirror leaves handling of the key up to the browser. A key handler function may return CodeMirror.Pass to indicate that it has decided not to handle the key, and other handlers (or the default behavior) should be given a turn.

Keys mapped to command names that start with the characters "go" (which should be used for cursor-movement actions) will be fired even when an extra Shift modifier is present (i.e. "Up": "goLineUp" matches both up and shift-up). This is used to easily implement shift-selection.

Keymaps can defer to each other by defining a fallthrough property. This indicates that when a key is not found in the map itself, one or more other maps should be searched. It can hold either a single keymap or an array of keymaps.

When a keymap contains a nofallthrough property set to true, keys matched against that map will be ignored if they don't match any of the bindings in the map (no further child maps will be tried, and the default effect of inserting a character will not occur).

Customized Styling

Up to a certain extent, CodeMirror's look can be changed by modifying style sheet files. The style sheets supplied by modes simply provide the colors for that mode, and can be adapted in a very straightforward way. To style the editor itself, it is possible to alter or override the styles defined in codemirror.css.

Some care must be taken there, since a lot of the rules in this file are necessary to have CodeMirror function properly. Adjusting colors should be safe, of course, and with some care a lot of other things can be changed as well. The CSS classes defined in this file serve the following roles:

The outer element of the editor. This should be used for the editor width, height, borders and positioning. Can also be used to set styles that should hold for everything inside the editor (such as font and font size), or to set a background.
Whether the editor scrolls (overflow: auto + fixed height). By default, it does. Setting the CodeMirror class to have height: auto and giving this class overflow-x: auto; overflow-y: hidden; will cause the editor to resize to fit its content.
Whenever the editor is focused, the top element gets this class. This is used to hide the cursor and give the selection a different color when the editor is not focused.
This is the backdrop for all gutters. Use it to set the default gutter background color, and optionally add a border on the right of the gutters.
Use this for giving a background or width to the line number gutter.
Used to style the actual individual line numbers. These won't be children of the CodeMirror-linenumbers (plural) element, but rather will be absolutely positioned to overlay it. Use this to set alignment and text properties for the line numbers.
The visible lines. This is where you specify vertical padding for the editor content.
The cursor is a block element that is absolutely positioned. You can make it look whichever way you want.
The selection is represented by span elements with this class.
CodeMirror-matchingbracket, CodeMirror-nonmatchingbracket
These are used to style matched (or unmatched) brackets.

If your page's style sheets do funky things to all div or pre elements (you probably shouldn't do that), you'll have to define rules to cancel these effects out again for elements under the CodeMirror class.

Themes are also simply CSS files, which define colors for various syntactic elements. See the files in the theme directory.

Programming API

A lot of CodeMirror features are only available through its API. Thus, you need to write code (or use add-ons) if you want to expose them to your users.

Whenever points in the document are represented, the API uses objects with line and ch properties. Both are zero-based. CodeMirror makes sure to 'clip' any positions passed by client code so that they fit inside the document, so you shouldn't worry too much about sanitizing your coordinates. If you give ch a value of null, or don't specify it, it will be replaced with the length of the specified line.

Methods prefixed with doc. can, unless otherwise specified, be called both on CodeMirror (editor) instances and CodeMirror.Doc instances. Methods prefixed with cm. are only available on CodeMirror instances.

Content manipulation methods

doc.getValue() → string
Get the current editor content. You can pass it an optional argument to specify the string to be used to separate lines (defaults to "\n").
Set the editor content.
doc.getRange(from, to) → string
Get the text between the given points in the editor, which should be {line, ch} objects. An optional third argument can be given to indicate the line separator string to use (defaults to "\n").
doc.replaceRange(string, from, to)
Replace the part of the document between from and to with the given string. from and to must be {line, ch} objects. to can be left off to simply insert the string at position from.
doc.getLine(n) → string
Get the content of line n.
doc.setLine(n, text)
Set the content of line n.
Remove the given line from the document.
doc.lineCount() → number
Get the number of lines in the editor.
doc.firstLine() → number
doc.lastLine() → number
Get the first and last lines of the editor. This will usually be zero and doc.lineCount() - 1 respectively, but for linked sub-views, or documents instantiated with a non-zero first line, it might return other values.
doc.getLineHandle(num) → lineHandle
Fetches the line handle for the given line number.
doc.getLineNumber(handle) → integer
Given a line handle, returns the current position of that line (or null when it is no longer in the document).
doc.eachLine(f) | doc.eachLine(start, end, f)
Iterate over the whole document, or if start and end line numbers are given, the range from start up to (not including) end, and call f for each line, passing the line handle. This is a faster way to visit a range of line handlers than calling getLineHandle for each of them. Note that line handles have a text property containing the line's content (as a string).
Set the editor content as 'clean', a flag that it will retain until it is edited, and which will be set again when such an edit is undone again. Useful to track whether the content needs to be saved.
doc.isClean() → boolean
Returns whether the document is currently clean (not modified since initialization or the last call to markClean).

Cursor and selection methods

doc.getSelection() → string
Get the currently selected code.
Replace the selection with the given string.
doc.getCursor(start) → object
start is a an optional string indicating which end of the selection to return. It may be "start", "end", "head" (the side of the selection that moves when you press shift+arrow), or "anchor" (the fixed side of the selection). Omitting the argument is the same as passing "head". A {line, ch} object will be returned.
doc.somethingSelected() → boolean
Return true if any text is selected.
Set the cursor position. You can either pass a single {line, ch} object, or the line and the character as two separate parameters.
doc.setSelection(anchor, head)
Set the selection range. anchor and head should be {line, ch} objects. head defaults to anchor when not given.
doc.extendSelection(pos, pos2)
Similar to setSelection, but will, if shift is held or the extending flag is set, move the head of the selection while leaving the anchor at its current place. pos2 is optional, and can be passed to ensure a region (for example a word or paragraph) will end up selected (in addition to whatever lies between that region and the current anchor).
Sets or clears the 'extending' flag, which acts similar to the shift key, in that it will cause cursor movement and calls to extendSelection to leave the selection anchor in place.
cm.findPosH(start, amount, unit, visually) → object
Used to find the target position for horizontal cursor motion. start is a {line, ch} object, amount an integer (may be negative), and unit one of the string "char", "column", or "word". Will return a position that is produced by moving amount times the distance specified by unit. When visually is true, motion in right-to-left text will be visual rather than logical. When the motion was clipped by hitting the end or start of the document, the returned value will have a hitSide property set to true.
cm.findPosV(start, amount, unit) → object
Similar to findPosH, but used for vertical motion. unit may be "line" or "page". The other arguments and the returned value have the same interpretation as they have in findPosH.

Configuration methods

cm.setOption(option, value)
Change the configuration of the editor. option should the name of an option, and value should be a valid value for that option.
cm.getOption(option) → value
Retrieves the current value of the given option for this editor instance.
Attach an additional keymap to the editor. This is mostly useful for add-ons that need to register some key handlers without trampling on the extraKeys option. Maps added in this way have a lower precedence than extraKeys, a higher precedence than the base keyMap, and between them, the maps added earlier have a higher precedence than those added later.
Disable a keymap added with addKeyMap. Either pass in the keymap object itself, or a string, which will be compared against the name property of the active keymaps.
cm.addOverlay(mode, options)
Enable a highlighting overlay. This is a stateless mini-mode that can be used to add extra highlighting. For example, the search add-on uses it to highlight the term that's currently being searched. mode can be a mode spec or a mode object (an object with a token method). The option parameter is optional. If given it should be an object. Currently, only the opaque option is recognized. This defaults to off, but can be given to allow the overlay styling, when not null, to override the styling of the base mode entirely, instead of the two being applied together.
Pass this the exact argument passed for the mode parameter to addOverlay to remove an overlay again.
cm.on(type, func)
Register an event handler for the given event type (a string) on the editor instance. There is also a CodeMirror.on(object, type, func) version that allows registering of events on any object.
cm.off(type, func)
Remove an event handler on the editor instance. An equivalent CodeMirror.off(object, type, func) also exists.

Document management methods

Each editor is associated with an instance of CodeMirror.Doc, its document. A document represents the editor content, plus a selection, an undo history, and a mode. A document can only be associated with a single editor at a time. You can create new documents by calling the CodeMirror.Doc(text, mode, firstLineNumber) constructor. The last two arguments are optional and can be used to set a mode for the document and make it start at a line number other than 0, respectively.

cm.getDoc() → doc
Retrieve the currently active document from an editor.
doc.getEditor() → editor
Retrieve the editor associated with a document. May return null.
cm.swapDoc(doc) → doc
Attach a new document to the editor. Returns the old document, which is now no longer associated with an editor.
doc.copy(copyHistory) → doc
Create an identical copy of the given doc. When copyHistory is true, the history will also be copied. Can not be called directly on an editor.
doc.linkedDoc(options) → doc
Create a new document that's linked to the target document. Linked documents will stay in sync (changes to one are also applied to the other) until unlinked. These are the options that are supported:
sharedHist (boolean)
When turned on, the linked copy will share an undo history with the original. Thus, something done in one of the two can be undone in the other, and vice versa.
from, to (integer)
Can be given to make the new document a subview of the original. Subviews only show a given range of lines. Note that line coordinates inside the subview will be consistent with those of the parent, so that for example a subview starting at line 10 will refer to its first line as line 10, not 0.
mode (mode spec)
By default, the new document inherits the mode of the parent. This option can be set to a mode spec to give it a different mode.
Break the link between two documents. After calling this, changes will no longer propagate between the documents, and, if they had a shared history, the history will become separate.
Will call the given function for all documents linked to the target document. It will be passed two arguments, the linked document and a boolean indicating whether that document shares history with the target.

History-related methods

Undo one edit (if any undo events are stored).
Redo one undone edit.
doc.historySize() → object
Returns an object with {undo, redo} properties, both of which hold integers, indicating the amount of stored undo and redo operations.
Clears the editor's undo history.
doc.getHistory() → object
Get a (JSON-serializeable) representation of the undo history.
Replace the editor's undo history with the one provided, which must be a value as returned by getHistory. Note that this will have entirely undefined results if the editor content isn't also the same as it was when getHistory was called.

Text-marking methods

doc.markText(from, to, options) → object
Can be used to mark a range of text with a specific CSS class name. from and to should be {line, ch} objects. The options parameter is optional. When given, it should be an object that may contain the following configuration options:
className (string)
Assigns a CSS class to the marked stretch of text.
inclusiveLeft (boolean)
Determines whether text inserted on the left of the marker will end up inside or outside of it.
inclusiveRight (boolean)
Like inclusiveLeft, but for the right side.
atomic (boolean)
Atomic ranges act as a single unit when cursor movement is concerned—i.e. it is impossible to place the cursor inside of them. In atomic ranges, inclusiveLeft and inclusiveRight have a different meaning—they will prevent the cursor from being placed respectively directly before and directly after the range.
collapsed (boolean)
Collapsed ranges do not show up in the display. Setting a range to be collapsed will automatically make it atomic.
clearOnEnter (boolean)
When enabled, will cause the mark to clear itself whenever the cursor enters its range. This is mostly useful for text-replacement widgets that need to 'snap open' when the user tries to edit them. A the "clear" event fired on the range handle can be used to be notified when this happens.
replacedWith (dom node)
Use a given node to display this range. Implies both collapsed and atomic. The given DOM node must be an inline element (as opposed to a block element).
A read-only span can, as long as it is not cleared, not be modified except by calling setValue to reset the whole document. Note: adding a read-only span currently clears the undo history of the editor, because existing undo events being partially nullified by read-only spans would corrupt the history (in the current implementation).
Can be used to specify an extra CSS class to be applied to the leftmost span that is part of the marker.
Equivalent to startStyle, but for the rightmost span.
When the target document is linked to other documents, you can set shared to true to make the marker appear in all documents. By default, a marker appears only in its target document.
The method will return an object that represents the marker (with constuctor CodeMirror.TextMarker), which exposes three methods: clear(), to remove the mark, find(), which returns a {from, to} object (both holding document positions), indicating the current position of the marked range, or undefined if the marker is no longer in the document, and finally getOptions(copyWidget), which returns an object representing the options for the marker. If copyWidget is given an true, it will clone the value of the replacedWith option, if any.
doc.setBookmark(pos, options) → object
Inserts a bookmark, a handle that follows the text around it as it is being edited, at the given position. A bookmark has two methods find() and clear(). The first returns the current position of the bookmark, if it is still in the document, and the second explicitly removes the bookmark. The options argument is optional. If given, the following properties are recognized:
Can be used to display a DOM node at the current location of the bookmark (analogous to the replacedWith option to markText).
By default, text typed when the cursor is on top of the bookmark will end up to the right of the bookmark. Set this option to true to make it go to the left instead.
doc.findMarksAt(pos) → array
Returns an array of all the bookmarks and marked ranges present at the given position.
doc.getAllMarks() → array
Returns an array containing all marked ranges in the document.

Widget, gutter, and decoration methods

cm.setGutterMarker(line, gutterID, value) → lineHandle
Sets the gutter marker for the given gutter (identified by its CSS class, see the gutters option) to the given value. Value can be either null, to clear the marker, or a DOM element, to set it. The DOM element will be shown in the specified gutter next to the specified line.
Remove all gutter markers in the gutter with the given ID.
cm.addLineClass(line, where, class) → lineHandle
Set a CSS class name for the given line. line can be a number or a line handle. where determines to which element this class should be applied, can can be one of "text" (the text element, which lies in front of the selection), "background" (a background element that will be behind the selection), or "wrap" (the wrapper node that wraps all of the line's elements, including gutter elements). class should be the name of the class to apply.
cm.removeLineClass(line, where, class) → lineHandle
Remove a CSS class from a line. line can be a line handle or number. where should be one of "text", "background", or "wrap" (see addLineClass). class can be left off to remove all classes for the specified node, or be a string to remove only a specific class.
cm.lineInfo(line) → object
Returns the line number, text content, and marker status of the given line, which can be either a number or a line handle. The returned object has the structure {line, handle, text, gutterMarkers, textClass, bgClass, wrapClass, widgets}, where gutterMarkers is an object mapping gutter IDs to marker elements, and widgets is an array of line widgets attached to this line, and the various class properties refer to classes added with addLineClass.
cm.addWidget(pos, node, scrollIntoView)
Puts node, which should be an absolutely positioned DOM node, into the editor, positioned right below the given {line, ch} position. When scrollIntoView is true, the editor will ensure that the entire node is visible (if possible). To remove the widget again, simply use DOM methods (move it somewhere else, or call removeChild on its parent).
cm.addLineWidget(line, node, options) → object
Adds a line widget, an element shown below a line, spanning the whole of the editor's width, and moving the lines below it downwards. line should be either an integer or a line handle, and node should be a DOM node, which will be displayed below the given line. options, when given, should be an object that configures the behavior of the widget. The following options are supported (all default to false):
coverGutter (boolean)
Whether the widget should cover the gutter.
noHScroll (boolean)
Whether the widget should stay fixed in the face of horizontal scrolling.
above (boolean)
Causes the widget to be placed above instead of below the text of the line.
showIfHidden (boolean)
When true, will cause the widget to be rendered even if the line it is associated with is hidden.
Note that the widget node will become a descendant of nodes with CodeMirror-specific CSS classes, and those classes might in some cases affect it. This method returns an object that represents the widget placement. It'll have a line property pointing at the line handle that it is associated with, and the following methods:
Removes the widget.
Call this if you made some change to the widget's DOM node that might affect its height. It'll force CodeMirror to update the height of the line that contains the widget.

Sizing, scrolling and positioning methods

cm.setSize(width, height)
Programatically set the size of the editor (overriding the applicable CSS rules). width and height height can be either numbers (interpreted as pixels) or CSS units ("100%", for example). You can pass null for either of them to indicate that that dimension should not be changed.
cm.scrollTo(x, y)
Scroll the editor to a given (pixel) position. Both arguments may be left as null or undefined to have no effect.
Get an {left, top, width, height, clientWidth, clientHeight} object that represents the current scroll position, the size of the scrollable area, and the size of the visible area (minus scrollbars).
Scrolls the given element into view. pos may be either a {line, ch} position, referring to a given character, null, to refer to the cursor, or a {left, top, right, bottom} object, in editor-local coordinates.
cm.cursorCoords(where, mode) → object
Returns an {left, top, bottom} object containing the coordinates of the cursor position. If mode is "local", they will be relative to the top-left corner of the editable document. If it is "page" or not given, they are relative to the top-left corner of the page. where can be a boolean indicating whether you want the start (true) or the end (false) of the selection, or, if a {line, ch} object is given, it specifies the precise position at which you want to measure.
cm.charCoords(pos, mode) → object
Returns the position and dimensions of an arbitrary character. pos should be a {line, ch} object. This differs from cursorCoords in that it'll give the size of the whole character, rather than just the position that the cursor would have when it would sit at that position.
cm.coordsChar(object) → pos
Given an {left, top} object (in page coordinates), returns the {line, ch} position that corresponds to it.
cm.defaultTextHeight() → number
Returns the line height of the default font for the editor.
cm.getViewport() → object
Returns a {from, to} object indicating the start (inclusive) and end (exclusive) of the currently rendered part of the document. In big documents, when most content is scrolled out of view, CodeMirror will only render the visible part, and a margin around it. See also the viewportChange event.
If your code does something to change the size of the editor element (window resizes are already listened for), or unhides it, you should probably follow up by calling this method to ensure CodeMirror is still looking as intended.

Mode, state, and token-related methods

When writing language-aware functionality, it can often be useful to hook into the knowledge thate the CodeMirror language mode has. See the section on modes for a more detailed description of how these work.

doc.getMode() → object
Gets the mode object for the editor. Note that this is distinct from getOption("mode"), which gives you the mode specification, rather than the resolved, instantiated mode object.
cm.getTokenAt(pos) → object
Retrieves information about the token the current mode found before the given position (a {line, ch} object). The returned object has the following properties:
The character (on the given line) at which the token starts.
The character at which the token ends.
The token's string.
The token type the mode assigned to the token, such as "keyword" or "comment" (may also be null).
The mode's state at the end of this token.
cm.getStateAfter(line) → state
Returns the mode's parser state, if any, at the end of the given line number. If no line number is given, the state at the end of the document is returned. This can be useful for storing parsing errors in the state, or getting other kinds of contextual information for a line.

Miscellaneous methods

cm.operation(func) → result
CodeMirror internally buffers changes and only updates its DOM structure after it has finished performing some operation. If you need to perform a lot of operations on a CodeMirror instance, you can call this method with a function argument. It will call the function, buffering up all changes, and only doing the expensive update after the function returns. This can be a lot faster. The return value from this method will be the return value of your function.
cm.indentLine(line, dir)
Adjust the indentation of the given line. The second argument (which defaults to "smart") may be one of:
Base indentation on the indentation of the previous line.
Use the mode's smart indentation if available, behave like "prev" otherwise.
Increase the indentation of the line by one indent unit.
Reduce the indentation of the line.
doc.posFromIndex(index) → object
Calculates and returns a {line, ch} object for a zero-based index who's value is relative to the start of the editor's text. If the index is out of range of the text then the returned object is clipped to start or end of the text respectively.
doc.indexFromPos(object) → number
The reverse of posFromIndex.
Give the editor focus.
cm.getInputField() → textarea
Returns the hidden textarea used to read input.
cm.getWrapperElement() → node
Returns the DOM node that represents the editor, and controls its size. Remove this from your tree to delete an editor instance.
cm.getScrollerElement() → node
Returns the DOM node that is responsible for the scrolling of the editor.
cm.getGutterElement() → node
Fetches the DOM node that contains the editor gutters.

Static properties

The CodeMirror object itself provides several useful properties. Firstly, its version property contains a string that indicates the version of the library. For releases, this simply contains "major.minor" (for example "2.33". For beta versions, " B" (space, capital B) is added at the end of the string, for development snapshots, " +" (space, plus) is added.

The CodeMirror.fromTextArea method provides another way to initialize an editor. It takes a textarea DOM node as first argument and an optional configuration object as second. It will replace the textarea with a CodeMirror instance, and wire up the form of that textarea (if any) to make sure the editor contents are put into the textarea when the form is submitted. A CodeMirror instance created this way has three additional methods:

Copy the content of the editor into the textarea.
Remove the editor, and restore the original textarea (with the editor's current content).
cm.getTextArea() → textarea
Returns the textarea that the instance was based on.

If you want to define extra methods in terms of the CodeMirror API, it is possible to use CodeMirror.defineExtension(name, value). This will cause the given value (usually a method) to be added to all CodeMirror instances created from then on.

Similarly, CodeMirror.defineOption(name, default, updateFunc) can be used to define new options for CodeMirror. The updateFunc will be called with the editor instance and the new value when an editor is initialized, and whenever the option is modified through setOption.

If your extention just needs to run some code whenever a CodeMirror instance is initialized, use CodeMirror.defineInitHook. Give it a function as its only argument, and from then on, that function will be called (with the instance as argument) whenever a new CodeMirror instance is initialized.


The addon directory in the distribution contains a number of reusable components that implement extra editor functionality. In brief, they are:

Provides a very simple way to query users for text input. Adds an openDialog method to CodeMirror instances, which can be called with an HTML fragment that provides the prompt (should include an input tag), and a callback function that is called when text has been entered. Depends on addon/dialog/dialog.css.
Adds the getSearchCursor(query, start, caseFold) → cursor method to CodeMirror instances, which can be used to implement search/replace functionality. query can be a regular expression or a string (only strings will match across lines—if they contain newlines). start provides the starting position of the search. It can be a {line, ch} object, or can be left off to default to the start of the document. caseFold is only relevant when matching a string. It will cause the search to be case-insensitive. A search cursor has the following methods:
findNext(), findPrevious() → boolean
Search forward or backward from the current position. The return value indicates whether a match was found. If matching a regular expression, the return value will be the array returned by the match method, in case you want to extract matched groups.
from(), to() → object
These are only valid when the last call to findNext or findPrevious did not return false. They will return {line, ch} objects pointing at the start and end of the match.
Replaces the currently found match with the given text and adjusts the cursor position to reflect the replacement.
Implements the search commands. CodeMirror has keys bound to these by default, but will not do anything with them unless an implementation is provided. Depends on searchcursor.js, and will make use of openDialog when available to make prompting for search queries less ugly.
Defines an option matchBrackets which, when set to true, causes matching brackets to be highlighted whenever the cursor is next to them. It also adds a method matchBrackets that forces this to happen once, and a method findMatchingBracket that can be used to run the bracket-finding algorithm that this uses internally.
Defines an option autoCloseBrackets that will auto-close brackets and quotes when typed. By default, it'll auto-close ()[]{}''"", but you can pass it a string similar to that (containing pairs of matching characters) to customize it. Demo here.
Helps with code folding. See the demo for an example. Call CodeMirror.newFoldFunction with a range-finder helper function to create a function that will, when applied to a CodeMirror instance and a line number, attempt to fold or unfold the block starting at the given line. A range-finder is a language-specific function that also takes an instance and a line number, and returns an range to be folded, or null if no block is started on that line. This file provides CodeMirror.braceRangeFinder, which finds blocks in brace languages (JavaScript, C, Java, etc), CodeMirror.indentRangeFinder, for languages where indentation determines block structure (Python, Haskell), and CodeMirror.tagRangeFinder, for XML-style languages.
Another approach to folding. See demo. Allows the user to select a range to fold by clicking in the gutter.
Can be used to run a CodeMirror mode over text without actually opening an editor instance. See the demo for an example. There are alternate versions of the file avaible for running stand-alone (without including all of CodeMirror) and for running under node.js.
Mode combinator that can be used to extend a mode with an 'overlay' — a secondary mode is run over the stream, along with the base mode, and can color specific pieces of text without interfering with the base mode. Defines CodeMirror.overlayMode, which is used to create such a mode. See this demo for a detailed example.
Mode combinator that can be used to easily 'multiplex' between several modes. Defines CodeMirror.multiplexingMode which, when given as first argument a mode object, and as other arguments any number of {open, close, mode [, delimStyle]} objects, will return a mode object that starts parsing using the mode passed as first argument, but will switch to another mode as soon as it encounters a string that occurs in one of the open fields of the passed objects. When in a sub-mode, it will go back to the top mode again when the close string is encountered. Pass "\n" for open or close if you want to switch on a blank line. When delimStyle is specified, it will be the token style returned for the delimiter tokens. The outer mode will not see the content between the delimiters. See this demo for an example.
Provides a framework for showing autocompletion hints. Defines CodeMirror.showHint, which takes a CodeMirror instance and a hinting function, and pops up a widget that allows the user to select a completion. Hinting functions are function that take an editor instance, and return a {list, from, to} object, where list is an array of strings (the completions), and from and to give the start and end of the token that is being completed. Depends on addon/hint/show-hint.css. See the other files in the addon/hint for hint sources for various languages. Check out the demo for an example.
Adds a highlightSelectionMatches option that can be enabled to highlight all instances of a currently selected word. Demo here.
Defines an interface component for showing linting warnings, with pluggable warning sources (see json-lint.js and javascript-lint.js in the same directory). Defines a lintWith option that can be set to a warning source (for example CodeMirror.javascriptValidator). Depends on addon/lint/lint.css. A demo can be found here.
Causes the selected text to be marked with the CSS class CodeMirror-selectedtext when the styleSelectedText option is enabled. Useful to change the colour of the selection (in addition to the background), like in this demo.
Defines a styleActiveLine option that, when enabled, gives the wrapper of the active line the class CodeMirror-activeline, and adds a background with the class CodeMirror-activeline-background. is enabled. See the demo.
Provides utility functions for adding automatic tag closing to XML modes. See the demo.
Defines a CodeMirror.requireMode(modename, callback) function that will try to load a given mode and call the callback when it succeeded. You'll have to set CodeMirror.modeURL to a string that mode paths can be constructed from, for example "mode/%N/%N.js"—the %N's will be replaced with the mode name. Also defines CodeMirror.autoLoadMode(instance, mode), which will ensure the given mode is loaded and cause the given editor instance to refresh its mode when the loading succeeded. See the demo.
Adds a command called newlineAndIndentContinueComment that you can bind Enter to in order to have the editor prefix new lines inside C-like block comments with an asterisk.

Writing CodeMirror Modes

Modes typically consist of a single JavaScript file. This file defines, in the simplest case, a lexer (tokenizer) for your language—a function that takes a character stream as input, advances it past a token, and returns a style for that token. More advanced modes can also handle indentation for the language.

The mode script should call CodeMirror.defineMode to register itself with CodeMirror. This function takes two arguments. The first should be the name of the mode, for which you should use a lowercase string, preferably one that is also the name of the files that define the mode (i.e. "xml" is defined in xml.js). The second argument should be a function that, given a CodeMirror configuration object (the thing passed to the CodeMirror function) and an optional mode configuration object (as in the mode option), returns a mode object.

Typically, you should use this second argument to defineMode as your module scope function (modes should not leak anything into the global scope!), i.e. write your whole mode inside this function.

The main responsibility of a mode script is parsing the content of the editor. Depending on the language and the amount of functionality desired, this can be done in really easy or extremely complicated ways. Some parsers can be stateless, meaning that they look at one element (token) of the code at a time, with no memory of what came before. Most, however, will need to remember something. This is done by using a state object, which is an object that is always passed when reading a token, and which can be mutated by the tokenizer.

Modes that use a state must define a startState method on their mode object. This is a function of no arguments that produces a state object to be used at the start of a document.

The most important part of a mode object is its token(stream, state) method. All modes must define this method. It should read one token from the stream it is given as an argument, optionally update its state, and return a style string, or null for tokens that do not have to be styled. For your styles, you are encouraged to use the 'standard' names defined in the themes (without the cm- prefix). If that fails, it is also possible to come up with your own and write your own CSS theme file.

The stream object that's passed to token encapsulates a line of code (tokens may never span lines) and our current position in that line. It has the following API:

eol() → boolean
Returns true only if the stream is at the end of the line.
sol() → boolean
Returns true only if the stream is at the start of the line.
peek() → character
Returns the next character in the stream without advancing it. Will return an null at the end of the line.
next() → character
Returns the next character in the stream and advances it. Also returns null when no more characters are available.
eat(match) → character
match can be a character, a regular expression, or a function that takes a character and returns a boolean. If the next character in the stream 'matches' the given argument, it is consumed and returned. Otherwise, undefined is returned.
eatWhile(match) → boolean
Repeatedly calls eat with the given argument, until it fails. Returns true if any characters were eaten.
eatSpace() → boolean
Shortcut for eatWhile when matching white-space.
Moves the position to the end of the line.
skipTo(ch) → boolean
Skips to the next occurrence of the given character, if found on the current line (doesn't advance the stream if the character does not occur on the line). Returns true if the character was found.
match(pattern, consume, caseFold) → boolean
Act like a multi-character eat—if consume is true or not given—or a look-ahead that doesn't update the stream position—if it is false. pattern can be either a string or a regular expression starting with ^. When it is a string, caseFold can be set to true to make the match case-insensitive. When successfully matching a regular expression, the returned value will be the array returned by match, in case you need to extract matched groups.
Backs up the stream n characters. Backing it up further than the start of the current token will cause things to break, so be careful.
column() → integer
Returns the column (taking into account tabs) at which the current token starts.
indentation() → integer
Tells you how far the current line has been indented, in spaces. Corrects for tab characters.
current() → string
Get the string between the start of the current token and the current stream position.

By default, blank lines are simply skipped when tokenizing a document. For languages that have significant blank lines, you can define a blankLine(state) method on your mode that will get called whenever a blank line is passed over, so that it can update the parser state.

Because state object are mutated, and CodeMirror needs to keep valid versions of a state around so that it can restart a parse at any line, copies must be made of state objects. The default algorithm used is that a new state object is created, which gets all the properties of the old object. Any properties which hold arrays get a copy of these arrays (since arrays tend to be used as mutable stacks). When this is not correct, for example because a mode mutates non-array properties of its state object, a mode object should define a copyState method, which is given a state and should return a safe copy of that state.

If you want your mode to provide smart indentation (through the indentLine method and the indentAuto and newlineAndIndent commands, to which keys can be bound), you must define an indent(state, textAfter) method on your mode object.

The indentation method should inspect the given state object, and optionally the textAfter string, which contains the text on the line that is being indented, and return an integer, the amount of spaces to indent. It should usually take the indentUnit option into account. An indentation method may return CodeMirror.Pass to indicate that it could not come up with a precise indentation.

Finally, a mode may define an electricChars property, which should hold a string containing all the characters that should trigger the behaviour described for the electricChars option.

So, to summarize, a mode must provide a token method, and it may provide startState, copyState, and indent methods. For an example of a trivial mode, see the diff mode, for a more involved example, see the C-like mode.

Sometimes, it is useful for modes to nest—to have one mode delegate work to another mode. An example of this kind of mode is the mixed-mode HTML mode. To implement such nesting, it is usually necessary to create mode objects and copy states yourself. To create a mode object, there are CodeMirror.getMode(options, parserConfig), where the first argument is a configuration object as passed to the mode constructor function, and the second argument is a mode specification as in the mode option. To copy a state object, call CodeMirror.copyState(mode, state), where mode is the mode that created the given state.

In a nested mode, it is recommended to add an extra methods, innerMode which, given a state object, returns a {state, mode} object with the inner mode and its state for the current position. These are used by utility scripts such as the autoformatter and the tag closer to get context information. Use the CodeMirror.innerMode helper function to, starting from a mode and a state, recursively walk down to the innermost mode and state.

To make indentation work properly in a nested parser, it is advisable to give the startState method of modes that are intended to be nested an optional argument that provides the base indentation for the block of code. The JavaScript and CSS parser do this, for example, to allow JavaScript and CSS code inside the mixed-mode HTML mode to be properly indented.

It is possible, and encouraged, to associate your mode, or a certain configuration of your mode, with a MIME type. For example, the JavaScript mode associates itself with text/javascript, and its JSON variant with application/json. To do this, call CodeMirror.defineMIME(mime, modeSpec), where modeSpec can be a string or object specifying a mode, as in the mode option.

Sometimes, it is useful to add or override mode object properties from external code. The CodeMirror.extendMode can be used to add properties to mode objects produced for a specific mode. Its first argument is the name of the mode, its second an object that specifies the properties that should be added. This is mostly useful to add utilities that can later be looked up through getMode.