Document (engine/view)

@ckeditor/ckeditor5-engine/src/view/document

class

Document class creates an abstract layer over the content editable area, contains a tree of view elements and view selection associated with this document.

Filtering

Public
Inherited
Mixed
Protected
Private
Deprecated

Properties

isComposing : Boolean

readonly observable

True if composition is in progress inside the document.

See source

This property is updated by the CompositionObserver. If the CompositionObserver is disabled this property will not change.
isFocused : Boolean

readonly observable

True if document is focused.

See source

This property is updated by the FocusObserver. If the FocusObserver is disabled this property will not change.
isReadOnly : Boolean

observable

Defines whether document is in read-only mode.

See source

When document is read-ony then all roots are read-only as well and caret placed inside this root is hidden.
roots : Collection

readonly

Roots of the view tree. Collection of the view elements.

See source

View roots are created as a result of binding between roots and roots and this is handled by EditingController, so to create view root we need to create model root using createRoot.
selection : DocumentSelection

readonly

Selection done on this document.

See source
stylesProcessor : StylesProcessor

readonly

The styles processor instance used by this document when normalizing styles.

See source
_postFixers : Set

private

Post-fixer callbacks registered to the view document.

See source

Methods

constructor( stylesProcessor )

Creates a Document instance.

See source

Parameters

stylesProcessor : StylesProcessor

The styles processor instance.
bind( bindProperties ) → Object

mixed
Binds observable properties to other objects implementing the Observable interface.

See source
Read more in the dedicated guide covering the topic of property bindings with some additional examples.

Consider two objects: a button and an associated command (both Observable).

A simple property binding could be as follows:
```
button.bind( 'isEnabled' ).to( command, 'isEnabled' );
```
or even shorter:
```
button.bind( 'isEnabled' ).to( command );
```
which works in the following way:
- button.isEnabled instantly equals command.isEnabled,
- whenever command.isEnabled changes, button.isEnabled will immediately reflect its value.
Note: To release the binding, use unbind.

You can also "rename" the property in the binding by specifying the new name in the to() chain:
```
button.bind( 'isEnabled' ).to( command, 'isWorking' );
```
It is possible to bind more than one property at a time to shorten the code:
```
button.bind( 'isEnabled', 'value' ).to( command );
```
which corresponds to:
```
button.bind( 'isEnabled' ).to( command );
button.bind( 'value' ).to( command );
```
The binding can include more than one observable, combining multiple data sources in a custom callback:
```
button.bind( 'isEnabled' ).to( command, 'isEnabled', ui, 'isVisible',
    ( isCommandEnabled, isUIVisible ) => isCommandEnabled && isUIVisible );
```
It is also possible to bind to the same property in an array of observables. To bind a button to multiple commands (also Observables) so that each and every one of them must be enabled for the button to become enabled, use the following code:
```
button.bind( 'isEnabled' ).toMany( [ commandA, commandB, commandC ], 'isEnabled',
    ( isAEnabled, isBEnabled, isCEnabled ) => isAEnabled && isBEnabled && isCEnabled );
```
Parameters

bindProperties : String

Observable properties that will be bound to other observable(s).

Returns

Object

The bind chain with the to() and toMany() methods.
decorate( methodName )

mixed
Turns the given methods of this object into event-based ones. This means that the new method will fire an event (named after the method) and the original action will be plugged as a listener to that event.

See source
Read more in the dedicated guide covering the topic of decorating methods with some additional examples.

Decorating the method does not change its behavior (it only adds an event), but it allows to modify it later on by listening to the method's event.

For example, to cancel the method execution the event can be stopped:
```
class Foo {
    constructor() {
        this.decorate( 'method' );
    }

    method() {
        console.log( 'called!' );
    }
}

const foo = new Foo();
foo.on( 'method', ( evt ) => {
    evt.stop();
}, { priority: 'high' } );

foo.method(); // Nothing is logged.
```
Note: The high priority listener has been used to execute this particular callback before the one which calls the original method (which uses the "normal" priority).

It is also possible to change the returned value:
```
foo.on( 'method', ( evt ) => {
    evt.return = 'Foo!';
} );

foo.method(); // -> 'Foo'
```
Finally, it is possible to access and modify the arguments the method is called with:
```
method( a, b ) {
    console.log( `${ a }, ${ b }`  );
}

// ...

foo.on( 'method', ( evt, args ) => {
    args[ 0 ] = 3;

    console.log( args[ 1 ] ); // -> 2
}, { priority: 'high' } );

foo.method( 1, 2 ); // -> '3, 2'
```
Parameters

methodName : String

Name of the method to decorate.
delegate( events ) → EmitterMixinDelegateChain

mixed
Delegates selected events to another Emitter. For instance:

See source
```
emitterA.delegate( 'eventX' ).to( emitterB );
emitterA.delegate( 'eventX', 'eventY' ).to( emitterC );
```
then eventX is delegated (fired by) emitterB and emitterC along with data:
```
emitterA.fire( 'eventX', data );
```
and eventY is delegated (fired by) emitterC along with data:
```
emitterA.fire( 'eventY', data );
```
Parameters

events : String

Event names that will be delegated to another emitter.

Returns

EmitterMixinDelegateChain
destroy()

Destroys this instance. Makes sure that all observers are destroyed and listeners removed.

See source
fire( eventOrInfo, [ args ] ) → *

mixed

Fires an event, executing all callbacks registered for it.

See source

The first parameter passed to callbacks is an EventInfo object, followed by the optional args provided in the fire() method call.

Parameters

eventOrInfo : String | EventInfo

The name of the event or EventInfo object if event is delegated.

[ args ] : *

Additional arguments to be passed to the callbacks.

Returns

*

By default the method returns undefined. However, the return value can be changed by listeners through modification of the evt.return's property (the event info is the first param of every callback).
getRoot( [ name ] ) → RootEditableElement | null

Gets a view root element with the specified name. If the name is not specific "main" root is returned.

See source

Parameters

[ name ] : String

Name of the root.

Defaults to 'main'

Returns

RootEditableElement | null

The view root element with the specified name or null when there is no root of given name.
listenTo( emitter, event, callback, [ options ] = { [options.priority] } )

mixed
Registers a callback function to be executed when an event is fired in a specific (emitter) object.

See source
Events can be grouped in namespaces using :. When namespaced event is fired, it additionally fires all callbacks for that namespace.
```
// myEmitter.on( ... ) is a shorthand for myEmitter.listenTo( myEmitter, ... ).
myEmitter.on( 'myGroup', genericCallback );
myEmitter.on( 'myGroup:myEvent', specificCallback );

// genericCallback is fired.
myEmitter.fire( 'myGroup' );
// both genericCallback and specificCallback are fired.
myEmitter.fire( 'myGroup:myEvent' );
// genericCallback is fired even though there are no callbacks for "foo".
myEmitter.fire( 'myGroup:foo' );
```
An event callback can stop the event and set the return value of the fire method.

Parameters

emitter : Emitter

The object that fires the event.

event : String

The name of the event.

callback : function

The function to be called on event.

[ options ] : Object

Additional options.

Properties

[ options.priority ] : PriorityString | Number

The priority of this event callback. The higher the priority value the sooner the callback will be fired. Events having the same priority are called in the order they were added.

Defaults to 'normal'

Defaults to {}
off( event, callback )

mixed

Stops executing the callback on the given event. Shorthand for this.stopListening( this, event, callback ).

See source

Parameters

event : String

The name of the event.

callback : function

The function to stop being called.
on( event, callback, [ options ] = { [options.priority] } )

mixed

Registers a callback function to be executed when an event is fired.

See source

Shorthand for this.listenTo( this, event, callback, options ) (it makes the emitter listen on itself).

Parameters

event : String

The name of the event.

callback : function

The function to be called on event.

[ options ] : Object

Additional options.

Properties

[ options.priority ] : PriorityString | Number

The priority of this event callback. The higher the priority value the sooner the callback will be fired. Events having the same priority are called in the order they were added.

Defaults to 'normal'

Defaults to {}
once( event, callback, [ options ] = { [options.priority] } )

mixed

Registers a callback function to be executed on the next time the event is fired only. This is similar to calling on followed by off in the callback.

See source

Parameters

event : String

The name of the event.

callback : function

The function to be called on event.

[ options ] : Object

Additional options.

Properties

[ options.priority ] : PriorityString | Number

The priority of this event callback. The higher the priority value the sooner the callback will be fired. Events having the same priority are called in the order they were added.

Defaults to 'normal'

Defaults to {}
registerPostFixer( postFixer )
Allows registering post-fixer callbacks. A post-fixers mechanism allows to update the view tree just before it is rendered to the DOM.

See source
Post-fixers are executed right after all changes from the outermost change block were applied but before the render event is fired. If a post-fixer callback made a change, it should return true. When this happens, all post-fixers are fired again to check if something else should not be fixed in the new document tree state.

View post-fixers are useful when you want to apply some fixes whenever the view structure changes. Keep in mind that changes executed in a view post-fixer should not break model-view mapping.

The types of changes which should be safe:
- adding or removing attribute from elements,
- changes inside of UI elements,
- marking some of the model elements to be re-converted.
Try to avoid changes which touch view structure:
- you should not add or remove nor wrap or unwrap any view elements,
- you should not change the editor data model in a view post-fixer.
As a parameter, a post-fixer callback receives a downcast writer.

Typically, a post-fixer will look like this:
```
editor.editing.view.document.registerPostFixer( writer => {
    if ( checkSomeCondition() ) {
        writer.doSomething();

        // Let other post-fixers know that something changed.
        return true;
    }
} );
```
Note that nothing happens right after you register a post-fixer (e.g. execute such a code in the console). That is because adding a post-fixer does not execute it. The post-fixer will be executed as soon as any change in the document needs to cause its rendering. If you want to re-render the editor's view after registering the post-fixer then you should do it manually by calling view.forceRender().

If you need to register a callback which is executed when DOM elements are already updated, use render event.

Parameters

postFixer : function
set( name, [ value ] )

mixed

Creates and sets the value of an observable property of this object. Such an property becomes a part of the state and is be observable.

See source

It accepts also a single object literal containing key/value pairs with properties to be set.

This method throws the observable-set-cannot-override error if the observable instance already have a property with the given property name. This prevents from mistakenly overriding existing properties and methods, but means that foo.set( 'bar', 1 ) may be slightly slower than foo.bar = 1.

Parameters

name : String | Object

The property's name or object with name=>value pairs.

[ value ] : *

The property's value (if name was passed in the first parameter).
stopDelegating( [ event ], [ emitter ] )

mixed
Stops delegating events. It can be used at different levels:

See source
- To stop delegating all events.
- To stop delegating a specific event to all emitters.
- To stop delegating a specific event to a specific emitter.
Parameters

[ event ] : String

The name of the event to stop delegating. If omitted, stops it all delegations.

[ emitter ] : Emitter

(requires event) The object to stop delegating a particular event to. If omitted, stops delegation of event to all emitters.
stopListening( [ emitter ], [ event ], [ callback ] )

mixed
Stops listening for events. It can be used at different levels:

See source
- To stop listening to a specific callback.
- To stop listening to a specific event.
- To stop listening to all events fired by a specific object.
- To stop listening to all events fired by all objects.
Parameters

[ emitter ] : Emitter

The object to stop listening to. If omitted, stops it for all objects.

[ event ] : String

(Requires the emitter) The name of the event to stop listening to. If omitted, stops it for all events from emitter.

[ callback ] : function

(Requires the event) The function to be removed from the call list for the given event.
unbind( [ unbindProperties ] )

mixed
Removes the binding created with bind.

See source
```
// Removes the binding for the 'a' property.
A.unbind( 'a' );

// Removes bindings for all properties.
A.unbind();
```
Parameters

[ unbindProperties ] : String

Observable properties to be unbound. All the bindings will be released if no properties are provided.
_callPostFixers( writer )

protected

Performs post-fixer loops. Executes post-fixer callbacks as long as none of them has done any changes to the model.

See source

Parameters

writer : DowncastWriter

Events

change:isComposing( eventInfo, name, value, oldValue )

Fired when the isComposing property changed value.

See source

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

name : String

Name of the changed property (isComposing).

value : Boolean

New value of the isComposing property with given key or null, if operation should remove property.

oldValue : Boolean

Old value of the isComposing property with given key or null, if property was not set before.
change:isFocused( eventInfo, name, value, oldValue )

Fired when the isFocused property changed value.

See source

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

name : String

Name of the changed property (isFocused).

value : Boolean

New value of the isFocused property with given key or null, if operation should remove property.

oldValue : Boolean

Old value of the isFocused property with given key or null, if property was not set before.
change:isReadOnly( eventInfo, name, value, oldValue )

Fired when the isReadOnly property changed value.

See source

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

name : String

Name of the changed property (isReadOnly).

value : Boolean

New value of the isReadOnly property with given key or null, if operation should remove property.

oldValue : Boolean

Old value of the isReadOnly property with given key or null, if property was not set before.
change:{property}( eventInfo, name, value, oldValue )

mixed
Fired when a property changed value.

See source
```
observable.set( 'prop', 1 );

observable.on( 'change:prop', ( evt, propertyName, newValue, oldValue ) => {
    console.log( `${ propertyName } has changed from ${ oldValue } to ${ newValue }` );
} );

observable.prop = 2; // -> 'prop has changed from 1 to 2'
```
Parameters

eventInfo : EventInfo

An object containing information about the fired event.

name : String

The property name.

value : *

The new property value.

oldValue : *

The previous property value.
beforeinput( eventInfo, data )
Fired before browser inputs (or deletes) some data.

See source
This event is available only on browsers which support DOM beforeinput event.

Introduced by InputObserver.

Note that because InputObserver is attached by the View this event is available by default.

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

data : DomEventData

Event data.

Related:
- InputObserver
blur( eventInfo, data )
Fired when one of the editables loses focus.

See source
Introduced by FocusObserver.

Note that because FocusObserver is attached by the View this event is available by default.

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

data : DomEventData

Event data.

Related:
- FocusObserver
click( eventInfo, data )
Fired when one of the editables has been clicked.

See source
Introduced by ClickObserver.

Note that this event is not available by default. To make it available ClickObserver needs to be added to View by a addObserver method.

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

data : DomEventData

Event data.

Related:
- ClickObserver
clipboardInput( eventInfo, data = { data.dataTransfer, data.targetRanges } )
Fired as a continuation of event-paste and event-drop events.

See source
It is a part of the "clipboard input pipeline".

Fired with a dataTransfer which comes from the clipboard and which content should be processed and inserted into the editor.

Note that this event is not available by default. To make it available ClipboardObserver needs to be added to Document by the addObserver method. It's done by the Clipboard feature. If it's not loaded, it must be done manually.

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

data : Object

Event data.

Properties

data.dataTransfer : DataTransfer

Data transfer instance.

data.targetRanges : Array.<Range>

Ranges which are the target of the operation (usually – into which the content should be inserted). If clipboard input was triggered by a paste operation, then these are the selection ranges. If by a drop operation, then it's the drop position (which can be different than the selection at the moment of drop).

Related:
- ClipboardObserver
- Clipboard
clipboardOutput( eventInfo, data )
Fired on event-copy and event-cut with a copy of selected content. The content can be processed before it ends up in the clipboard.

See source
It is a part of the "clipboard output pipeline".

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

data : ClipboardOutputEventData

Event data.

Related:
- ClipboardObserver
- Clipboard
compositionend( eventInfo, data )
Fired when composition ends inside one of the editables.

See source
Introduced by CompositionObserver.

Note that because CompositionObserver is attached by the View this event is available by default.

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

data : DomEventData

Event data.

Related:
- CompositionObserver
compositionstart( eventInfo, data )
Fired when composition starts inside one of the editables.

See source
Introduced by CompositionObserver.

Note that because CompositionObserver is attached by the View this event is available by default.

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

data : DomEventData

Event data.

Related:
- CompositionObserver
compositionupdate( eventInfo, data )
Fired when composition is updated inside one of the editables.

See source
Introduced by CompositionObserver.

Note that because CompositionObserver is attached by the View this event is available by default.

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

data : DomEventData

Event data.

Related:
- CompositionObserver
copy( eventInfo, data )
Fired when user copied content from one of the editables.

See source
Introduced by ClipboardObserver.

Note that this event is not available by default. To make it available ClipboardObserver needs to be added to Document by the addObserver method. It's done by the Clipboard feature. If it's not loaded, it must be done manually.

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

data : ClipboardEventData

Event data.

Related:
- ClipboardObserver
cut( eventInfo, data )
Fired when user cut content from one of the editables.

See source
Introduced by ClipboardObserver.

Note that this event is not available by default. To make it available ClipboardObserver needs to be added to Document by the addObserver method. It's done by the Clipboard feature. If it's not loaded, it must be done manually.

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

data : ClipboardEventData

Event data.

Related:
- ClipboardObserver
delete( eventInfo, data, data.direction, data.unit, data.sequence, [ data.selectionToRemove ] )

Event fired when the user tries to delete content (e.g. presses Delete or Backspace).

See source

Note: This event is fired by the observer (usually registered by the delete feature).

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

data : DomEventData

data.direction : 'forward' | 'delete'

The direction in which the deletion should happen.

data.unit : 'character' | 'word'

The "amount" of content that should be deleted.

data.sequence : Number

A number describing which subsequent delete event it is without the key being released. If it's 2 or more it means that the key was pressed and hold.

[ data.selectionToRemove ] : Selection

View selection which content should be removed. If not set, current selection should be used.
dragover( eventInfo, data )
Fired when user drags content over one of the editables.

See source
Introduced by ClipboardObserver.

Note that this event is not available by default. To make it available ClipboardObserver needs to be added to Document by the addObserver method. It's done by the Clipboard feature. If it's not loaded, it must be done manually.

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

data : ClipboardEventData

Event data.

Related:
- Document#event:clipboardInput
drop( eventInfo, data, dropRange )
Fired when user dropped content into one of the editables.

See source
Introduced by ClipboardObserver.

Note that this event is not available by default. To make it available ClipboardObserver needs to be added to Document by the addObserver method. It's done by the Clipboard feature. If it's not loaded, it must be done manually.

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

data : ClipboardEventData

Event data.

dropRange : Range

The position into which the content is dropped.

Related:
- Document#event:clipboardInput
enter( eventInfo, data, data.isSoft )

Event fired when the user presses the Enter key.

See source

Note: This event is fired by the observer (usually registered by the Enter feature and ShiftEnter feature).

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

data : DomEventData

data.isSoft : Boolean

Whether it's a soft enter (Shift+Enter) or hard enter (Enter).
focus( eventInfo, data )
Fired when one of the editables gets focus.

See source
Introduced by FocusObserver.

Note that because FocusObserver is attached by the View this event is available by default.

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

data : DomEventData

Event data.

Related:
- FocusObserver
imageLoaded( eventInfo, data )
Fired when an DOM element has been loaded in the DOM root.

See source
Introduced by ImageLoadObserver.

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

data : DomEventData

Event data.

Related:
- ImageLoadObserver
keydown( eventInfo, keyEventData )
Fired when a key has been pressed.

See source
Introduced by KeyObserver.

Note that because KeyObserver is attached by the View this event is available by default.

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

keyEventData : KeyEventData

Related:
- KeyObserver
keyup( eventInfo, keyEventData )
Fired when a key has been released.

See source
Introduced by KeyObserver.

Note that because KeyObserver is attached by the View this event is available by default.

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

keyEventData : KeyEventData

Related:
- KeyObserver
mousedown( eventInfo, data )
Fired when mouse button is pressed down on one of the editables.

See source
Introduced by MouseObserver.

Note that this event is not available by default. To make it available MouseObserver needs to be added to View by a addObserver method.

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

data : DomEventData

Event data.

Related:
- MouseObserver
mouseleave( eventInfo, data )
Fired when the mouse is moved out of one of the editables.

See source
Introduced by MouseEventsObserver.

Note that this event is not available by default. To make it available, MouseEventsObserver needs to be added to View using the addObserver method.

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

data : DomEventData

Event data.

Related:
- MouseEventsObserver
mousemove( eventInfo, data )
Fired when the mouse is moved over one of the editables.

See source
Introduced by MouseEventsObserver.

Note that this event is not available by default. To make it available, MouseEventsObserver needs to be added to View using the addObserver method.

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

data : DomEventData

Event data.

Related:
- MouseEventsObserver
mouseup( eventInfo, data )
Fired when the mouse button is released over one of the editables.

See source
Introduced by MouseEventsObserver.

Note that this event is not available by default. To make it available, MouseEventsObserver needs to be added to View using the addObserver method.

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

data : DomEventData

Event data.

Related:
- MouseEventsObserver
mutations( eventInfo, viewMutations, viewSelection )
Fired when mutation occurred. If tree view is not changed on this event, DOM will be reverted to the state before mutation, so all changes which should be applied, should be handled on this event.

See source
Introduced by MutationObserver.

Note that because MutationObserver is attached by the View this event is available by default.

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

viewMutations : Array.<(MutatedText | MutatedChildren)>

Array of mutations. For mutated texts it will be MutatedText and for mutated elements it will be MutatedChildren. You can recognize the type based on the type property.

viewSelection : Selection | null

View selection that is a result of converting DOM selection to view. Keep in mind that the DOM selection is already "updated", meaning that it already acknowledges changes done in mutation.

Related:
- MutationObserver
paste( eventInfo, data )
Fired when user pasted content into one of the editables.

See source
Introduced by ClipboardObserver.

Note that this event is not available by default. To make it available ClipboardObserver needs to be added to Document by the addObserver method. It's done by the Clipboard feature. If it's not loaded, it must be done manually.

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

data : ClipboardEventData

Event data.

Related:
- Document#event:clipboardInput
selectionChange( eventInfo, data = { data.oldSelection, data.newSelection, data.domSelection } )
Fired when selection has changed. This event is fired only when the selection change was the only change that happened in the document, and old selection is different then the new selection.

See source
Introduced by SelectionObserver.

Note that because SelectionObserver is attached by the View this event is available by default.

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

data : Object

Properties

data.oldSelection : DocumentSelection

Old View selection which is selection.

data.newSelection : Selection

New View selection which is converted DOM selection.

data.domSelection : Selection

Native DOM selection.

Related:
- SelectionObserver
selectionChangeDone( eventInfo, data = { data.oldSelection, data.newSelection, data.domSelection } )
Fired when selection stops changing.

See source
Introduced by SelectionObserver.

Note that because SelectionObserver is attached by the View this event is available by default.

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

data : Object

Properties

data.oldSelection : DocumentSelection

Old View selection which is selection.

data.newSelection : Selection

New View selection which is converted DOM selection.

data.domSelection : Selection

Native DOM selection.

Related:
- SelectionObserver
layoutChanged( eventInfo )

Event fired whenever document content layout changes. It is fired whenever content is rendered, but should be also fired by observers in case of other actions which may change layout, for instance when image loads.

See source

Parameters

eventInfo : EventInfo

An object containing information about the fired event.
set:{property}( eventInfo, name, value, oldValue )

mixed
Fired when a property value is going to be set but is not set yet (before the change event is fired).

See source
You can control the final value of the property by using the event's return property.
```
observable.set( 'prop', 1 );

observable.on( 'set:prop', ( evt, propertyName, newValue, oldValue ) => {
    console.log( `Value is going to be changed from ${ oldValue } to ${ newValue }` );
    console.log( `Current property value is ${ observable[ propertyName ] }` );

    // Let's override the value.
    evt.return = 3;
} );

observable.on( 'change:prop', ( evt, propertyName, newValue, oldValue ) => {
    console.log( `Value has changed from ${ oldValue } to ${ newValue }` );
} );

observable.prop = 2; // -> 'Value is going to be changed from 1 to 2'
                     // -> 'Current property value is 1'
                     // -> 'Value has changed from 1 to 3'
```
Note: Event is fired even when the new value is the same as the old value.

Parameters

eventInfo : EventInfo

An object containing information about the fired event.

name : String

The property name.

value : *

The new property value.

oldValue : *

The previous property value.

Document (engine/view)

Filtering

Properties

isComposing : Booleanmodule:engine/view/document~Document#isComposing

isFocused : Booleanmodule:engine/view/document~Document#isFocused

isReadOnly : Booleanmodule:engine/view/document~Document#isReadOnly

roots : Collectionmodule:engine/view/document~Document#roots

selection : DocumentSelectionmodule:engine/view/document~Document#selection

stylesProcessor : StylesProcessormodule:engine/view/document~Document#stylesProcessor

_postFixers : Setmodule:engine/view/document~Document#_postFixers

Methods

constructor( stylesProcessor )module:engine/view/document~Document#constructor

Parameters

bind( bindProperties ) → Objectmodule:engine/view/document~Document#bind

Parameters

Returns

decorate( methodName )module:engine/view/document~Document#decorate

Parameters

delegate( events ) → EmitterMixinDelegateChainmodule:engine/view/document~Document#delegate

Parameters

Returns

destroy()module:engine/view/document~Document#destroy

fire( eventOrInfo, [ args ] ) → *module:engine/view/document~Document#fire

Parameters

Returns

getRoot( [ name ] ) → RootEditableElement | nullmodule:engine/view/document~Document#getRoot

Parameters

Returns

listenTo( emitter, event, callback, [ options ] = { [options.priority] } )module:engine/view/document~Document#listenTo

Parameters

off( event, callback )module:engine/view/document~Document#off

Parameters

on( event, callback, [ options ] = { [options.priority] } )module:engine/view/document~Document#on

Parameters

once( event, callback, [ options ] = { [options.priority] } )module:engine/view/document~Document#once

Parameters

registerPostFixer( postFixer )module:engine/view/document~Document#registerPostFixer

Parameters

set( name, [ value ] )module:engine/view/document~Document#set

Parameters

stopDelegating( [ event ], [ emitter ] )module:engine/view/document~Document#stopDelegating

Parameters

stopListening( [ emitter ], [ event ], [ callback ] )module:engine/view/document~Document#stopListening

Parameters

unbind( [ unbindProperties ] )module:engine/view/document~Document#unbind

Parameters

_callPostFixers( writer )module:engine/view/document~Document#_callPostFixers

Parameters

Events

change:isComposing( eventInfo, name, value, oldValue )module:engine/view/document~Document#event:change:isComposing

Parameters

change:isFocused( eventInfo, name, value, oldValue )module:engine/view/document~Document#event:change:isFocused

Parameters

change:isReadOnly( eventInfo, name, value, oldValue )module:engine/view/document~Document#event:change:isReadOnly

Parameters

change:{property}( eventInfo, name, value, oldValue )module:engine/view/document~Document#event:change:{property}

Parameters

beforeinput( eventInfo, data )module:engine/view/document~Document#event:beforeinput

Parameters

Related:

blur( eventInfo, data )module:engine/view/document~Document#event:blur

Parameters

Related:

click( eventInfo, data )module:engine/view/document~Document#event:click

Parameters

Related:

clipboardInput( eventInfo, data = { data.dataTransfer, data.targetRanges } )module:engine/view/document~Document#event:clipboardInput

Parameters

Related:

clipboardOutput( eventInfo, data )module:engine/view/document~Document#event:clipboardOutput

Parameters

Related:

compositionend( eventInfo, data )module:engine/view/document~Document#event:compositionend

Parameters

Related:

compositionstart( eventInfo, data )module:engine/view/document~Document#event:compositionstart

Parameters

Related:

compositionupdate( eventInfo, data )module:engine/view/document~Document#event:compositionupdate

Parameters

`isComposing : Boolean`

`isFocused : Boolean`

`isReadOnly : Boolean`

`roots : Collection`

`selection : DocumentSelection`

`stylesProcessor : StylesProcessor`

`_postFixers : Set`

`constructor( stylesProcessor )`

`bind( bindProperties ) → Object`

`decorate( methodName )`

`delegate( events ) → EmitterMixinDelegateChain`

`destroy()`

`fire( eventOrInfo, [ args ] ) → *`

`getRoot( [ name ] ) → RootEditableElement | null`

`listenTo( emitter, event, callback, [ options ] = { [options.priority] } )`

`off( event, callback )`

`on( event, callback, [ options ] = { [options.priority] } )`

`once( event, callback, [ options ] = { [options.priority] } )`

`registerPostFixer( postFixer )`

`set( name, [ value ] )`

`stopDelegating( [ event ], [ emitter ] )`

`stopListening( [ emitter ], [ event ], [ callback ] )`

`unbind( [ unbindProperties ] )`

`_callPostFixers( writer )`

`change:isComposing( eventInfo, name, value, oldValue )`

`change:isFocused( eventInfo, name, value, oldValue )`

`change:isReadOnly( eventInfo, name, value, oldValue )`

`change:{property}( eventInfo, name, value, oldValue )`

`beforeinput( eventInfo, data )`

`blur( eventInfo, data )`

`click( eventInfo, data )`

`clipboardInput( eventInfo, data = { data.dataTransfer, data.targetRanges } )`

`clipboardOutput( eventInfo, data )`

`compositionend( eventInfo, data )`

`compositionstart( eventInfo, data )`

`compositionupdate( eventInfo, data )`

`copy( eventInfo, data )`

`cut( eventInfo, data )`

`delete( eventInfo, data, data.direction, data.unit, data.sequence, [ data.selectionToRemove ] )`

`dragover( eventInfo, data )`

`drop( eventInfo, data, dropRange )`

`enter( eventInfo, data, data.isSoft )`

`focus( eventInfo, data )`

`imageLoaded( eventInfo, data )`

`keydown( eventInfo, keyEventData )`

`keyup( eventInfo, keyEventData )`

`mousedown( eventInfo, data )`

`mouseleave( eventInfo, data )`

`mousemove( eventInfo, data )`

`mouseup( eventInfo, data )`

`mutations( eventInfo, viewMutations, viewSelection )`

`paste( eventInfo, data )`

`selectionChange( eventInfo, data = { data.oldSelection, data.newSelection, data.domSelection } )`

`selectionChangeDone( eventInfo, data = { data.oldSelection, data.newSelection, data.domSelection } )`

`layoutChanged( eventInfo )`

`set:{property}( eventInfo, name, value, oldValue )`