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OpenLayers · API reference

Modify

Quick answer

Check if a point can be inserted to the current linestring or polygon at the current pointer position.

Last verified 2026-11-03 · OpenLayers 10.3.1 · Cite this page
Runnable examplesChinese noteAll API topics

new Modify(options)

interaction/Modify.js, line 273
Name Type Description
condition Condition | undefined

A function that takes a MapBrowserEvent and returns a boolean to indicate whether that event will be considered to add or move a vertex to the sketch. Default is primaryAction.
deleteCondition Condition | undefined

A function that takes a MapBrowserEvent and returns a boolean to indicate whether that event should be handled. By default, singleClick with altKeyOnly results in a vertex deletion. This combination is handled by wrapping the two condition checks in a single function:

import { altKeyOnly, singleClick } from 'ol/events/condition.js';

function (event) {
  return altKeyOnly(event) && singleClick(event)
}
insertVertexCondition Condition | undefined

A function that takes a MapBrowserEvent and returns a boolean to indicate whether a new vertex should be added to the sketch features. Default is always.
pixelTolerance number (defaults to 10)

Pixel tolerance for considering the pointer close enough to a segment or vertex for editing.
style StyleLike | FlatStyleLike | undefined

Style used for the modification point or vertex. For linestrings and polygons, this will be the affected vertex, for circles a point along the circle, and for points the actual point. If not configured, the default edit style is used (see Style). When using a style function, the point feature passed to the function will have an existing property - indicating whether there is an existing vertex underneath or not, a features property - an array whose entries are the features that are being modified, and a geometries property - an array whose entries are the geometries that are being modified. Both arrays are in the same order. The geometries are only useful when modifying geometry collections, where the geometry will be the particular geometry from the collection that is being modified.
source VectorSource | undefined

The vector source with features to modify. If a vector source is not provided, a feature collection must be provided with the features option.
hitDetection boolean | BaseVectorLayer<any, any, any> | undefined

When configured, point features will be considered for modification based on their visual appearance, instead of being within the pixelTolerance from the pointer location. When a BaseVectorLayer is provided, only the rendered representation of the features on that layer will be considered.
features Collection<Feature> | undefined

The features the interaction works on. If a feature collection is not provided, a vector source must be provided with the source option.
filter FilterFunction | undefined

A function that takes a Feature and returns true if the feature may be modified or false otherwise.
trace boolean | Condition (defaults to false)

Trace a portion of another geometry. Tracing starts when two neighboring vertices are dragged onto a trace target, without any other modification in between..
traceSource VectorSource | undefined

Source for features to trace. If tracing is active and a traceSource is not provided, the interaction's source will be used. Tracing requires that the interaction is configured with either a traceSource or a source.
wrapX boolean (defaults to false)

Wrap the world horizontally on the sketch overlay.
snapToPointer boolean (defaults to !hitDetection)

The vertex, point or segment being modified snaps to the pointer coordinate when clicked within the pixelTolerance.
sharedVerticesEqual function | undefined

A function that takes two coordinates and returns whether they should be considered equal for vertex matching purposes. By default, all coordinate dimensions are compared. This is useful when features have mixed coordinate dimensions (e.g., XY and XYZ) but should still be treated as sharing vertices at the same 2D position.
Fires:
  • change (BaseEvent) - Generic change event. Triggered when the revision counter is increased.
  • change:active (ObjectEvent)
  • error (BaseEvent) - Generic error event. Triggered when an error occurs.
  • modifyend (ModifyEvent) - Triggered upon feature modification end
  • modifystart (ModifyEvent) - Triggered upon feature modification start
  • propertychange (ObjectEvent) - Triggered when a property is changed.

Extends

Observable Properties

Name Type Settable ObjectEvent type Description
active boolean yes change:active

true if the interaction is active, false otherwise.

Methods

canInsertPoint(){boolean}

interaction/Modify.js, line 2539

Check if a point can be inserted to the current linestring or polygon at the current pointer position.

Returns:
A point can be inserted at the current pointer position.

canRemovePoint(){boolean}

interaction/Modify.js, line 2321

Check if a point can be removed from the current linestring or polygon at the current pointer position.

Returns:
A point can be deleted at the current pointer position.

changed() inherited

Observable.js, line 72

Increases the revision counter and dispatches a 'change' event.

dispatchEvent(event){boolean | undefined} inherited

events/Target.js, line 85

Dispatches an event and calls all listeners listening for events of this type. The event parameter can either be a string or an Object with a type property.

Name Type Description
event BaseEvent | string

Event object.
Returns:
false if anyone called preventDefault on the event object or if any of the listeners returned false.

get(key){*} inherited

Object.js, line 136

Gets a value.

Name Type Description
key string

Key name.
Returns:
Value.

getActive(){boolean} inherited

interaction/Interaction.js, line 82

Return whether the interaction is currently active.

Returns:
true if the interaction is active, false otherwise.

getKeys(){Array.<string>} inherited

Object.js, line 149

Get a list of object property names.

Returns:
List of property names.

getMap(){Map | null} inherited

interaction/Interaction.js, line 91

Get the map associated with this interaction.

Returns:
Map.

getOverlay(){VectorLayer}

interaction/Modify.js, line 753

Get the overlay layer that this interaction renders the modification point or vertex to.

Returns:
Overlay layer.

getPointerCount(){number} inherited

interaction/Pointer.js, line 95

Returns the current number of pointers involved in the interaction, e.g. 2 when two fingers are used.

Returns:
The number of pointers.

getProperties(){NoInfer.<Properties>} inherited

Object.js, line 158

Get an object of all property names and values.

Returns:
Object.

getRevision(){number} inherited

Observable.js, line 83

Get the version number for this object. Each time the object is modified, its version number will be incremented.

Returns:
Revision.

insertPoint(coordinate){boolean}

interaction/Modify.js, line 2574

Inserts the vertex currently being pointed to the current linestring or polygon.

Name Type Description
coordinate Coordinate | undefined

If provided, the pointer will be set to the provided coordinate. If not, the current pointer coordinate will be used.
Returns:
A vertex was inserted.

on(type, listener){EventsKey | Array<EventsKey>} inherited

Observable.js, line 156

Listen for a certain type of event.

Name Type Description
type string | Array.<string>

The event type or array of event types.
listener function

The listener function.
Returns:
Unique key for the listener. If called with an array of event types as the first argument, the return will be an array of keys.

once(type, listener){EventsKey | Array<EventsKey>} inherited

Observable.js, line 168

Listen once for a certain type of event.

Name Type Description
type string | Array.<string>

The event type or array of event types.
listener function

The listener function.
Returns:
Unique key for the listener. If called with an array of event types as the first argument, the return will be an array of keys.

removePoint(coordinate){boolean}

interaction/Modify.js, line 2354

Removes the vertex currently being pointed from the current linestring or polygon.

Name Type Description
coordinate Coordinate | undefined

If provided, the pointer will be set to the provided coordinate. If not, the current pointer coordinate will be used.
Returns:
True when a vertex was removed.

set(key, value, silent) inherited

Object.js, line 218

Sets a value.

Name Type Description
key string

Key name.
value *

Value.
silent boolean | undefined

Update without triggering an event.

setActive(active)

interaction/Modify.js, line 726

Activate or deactivate the interaction.

Name Type Description
active boolean

Active.

setProperties(values, silent) inherited

Object.js, line 241

Sets a collection of key-value pairs. Note that this changes any existing properties and adds new ones (it does not remove any existing properties).

Name Type Description
values Partial.<NoInfer.<Properties>>

Values.
silent boolean | undefined

Update without triggering an event.

un(type, listener) inherited

Observable.js, line 177

Unlisten for a certain type of event.

Name Type Description
type string | Array.<string>

The event type or array of event types.
listener function

The listener function.

unset(key, silent) inherited

Object.js, line 265

Unsets a property.

Name Type Description
key string

Key name.
silent boolean | undefined

Unset without triggering an event.
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English reference text adapted from the official OpenLayers documentation, © OpenLayers contributors, licensed under BSD-2-Clause.
Original page: https://openlayers.org/en/latest/apidoc/module-ol_interaction_Modify-Modify.html · Chinese note: /openlayers/api/modify.html
Cite this page

Atlaslog (2026). Modify. https://www.jingweizhi.com/en/openlayers/api/modify.html (accessed 2026-11-03).