@ckeditor/ckeditor5-engine
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The editing engine of CKEditor 5 – the best browser-based rich text editor.
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JavaScript
/**
* @license Copyright (c) 2003-2025, CKSource Holding sp. z o.o. All rights reserved.
* For licensing, see LICENSE.md or https://ckeditor.com/legal/ckeditor-licensing-options
*/
import { ModelPosition, getTextNodeAtPosition, getNodeAfterPosition, getNodeBeforePosition } from './position.js';
import { ModelTextProxy } from './textproxy.js';
import { CKEditorError } from '@ckeditor/ckeditor5-utils';
/**
* Position iterator class. It allows to iterate forward and backward over the document.
*/
export class ModelTreeWalker {
/**
* Walking direction. Defaults `'forward'`.
*/
direction;
/**
* Iterator boundaries.
*
* When the iterator is walking `'forward'` on the end of boundary or is walking `'backward'`
* on the start of boundary, then `{ done: true }` is returned.
*
* If boundaries are not defined they are set before first and after last child of the root node.
*/
boundaries;
/**
* Flag indicating whether all consecutive characters with the same attributes should be
* returned as one {@link module:engine/model/textproxy~ModelTextProxy} (`true`) or one by one (`false`).
*/
singleCharacters;
/**
* Flag indicating whether iterator should enter elements or not. If the iterator is shallow child nodes of any
* iterated node will not be returned along with `elementEnd` tag.
*/
shallow;
/**
* Flag indicating whether iterator should ignore `elementEnd` tags. If the option is true walker will not
* return a parent node of the start position. If this option is `true` each {@link module:engine/model/element~ModelElement} will
* be returned once, while if the option is `false` they might be returned twice:
* for `'elementStart'` and `'elementEnd'`.
*/
ignoreElementEnd;
/**
* Iterator position. This is always static position, even if the initial position was a
* {@link module:engine/model/liveposition~ModelLivePosition live position}. If start position is not defined then position depends
* on {@link #direction}. If direction is `'forward'` position starts form the beginning, when direction
* is `'backward'` position starts from the end.
*/
_position;
/**
* Start boundary cached for optimization purposes.
*/
_boundaryStartParent;
/**
* End boundary cached for optimization purposes.
*/
_boundaryEndParent;
/**
* Parent of the most recently visited node. Cached for optimization purposes.
*/
_visitedParent;
/**
* Creates a range iterator. All parameters are optional, but you have to specify either `boundaries` or `startPosition`.
*
* @param options Object with configuration.
*/
constructor(options) {
if (!options || (!options.boundaries && !options.startPosition)) {
/**
* Neither boundaries nor starting position of a `TreeWalker` have been defined.
*
* @error model-tree-walker-no-start-position
*/
throw new CKEditorError('model-tree-walker-no-start-position', null);
}
const direction = options.direction || 'forward';
if (direction != 'forward' && direction != 'backward') {
/**
* Only `backward` and `forward` direction allowed.
*
* @error model-tree-walker-unknown-direction
*/
throw new CKEditorError('model-tree-walker-unknown-direction', options, { direction });
}
this.direction = direction;
this.boundaries = options.boundaries || null;
if (options.startPosition) {
this._position = options.startPosition.clone();
}
else {
this._position = ModelPosition._createAt(this.boundaries[this.direction == 'backward' ? 'end' : 'start']);
}
// Reset position stickiness in case it was set to other value, as the stickiness is kept after cloning.
this.position.stickiness = 'toNone';
this.singleCharacters = !!options.singleCharacters;
this.shallow = !!options.shallow;
this.ignoreElementEnd = !!options.ignoreElementEnd;
this._boundaryStartParent = this.boundaries ? this.boundaries.start.parent : null;
this._boundaryEndParent = this.boundaries ? this.boundaries.end.parent : null;
this._visitedParent = this.position.parent;
}
/**
* Iterable interface.
*
* @returns {Iterable.<module:engine/model/treewalker~ModelTreeWalkerValue>}
*/
[Symbol.iterator]() {
return this;
}
/**
* Iterator position. This is always static position, even if the initial position was a
* {@link module:engine/model/liveposition~ModelLivePosition live position}. If start position is not defined then position depends
* on {@link #direction}. If direction is `'forward'` position starts form the beginning, when direction
* is `'backward'` position starts from the end.
*/
get position() {
return this._position;
}
/**
* Moves {@link #position} in the {@link #direction} skipping values as long as the callback function returns `true`.
*
* For example:
*
* ```ts
* walker.skip( value => value.type == 'text' ); // <paragraph>[]foo</paragraph> -> <paragraph>foo[]</paragraph>
* walker.skip( () => true ); // Move the position to the end: <paragraph>[]foo</paragraph> -> <paragraph>foo</paragraph>[]
* walker.skip( () => false ); // Do not move the position.
* ```
*
* @param skip Callback function. Gets {@link module:engine/model/treewalker~ModelTreeWalkerValue} and should
* return `true` if the value should be skipped or `false` if not.
*/
skip(skip) {
let done, value, prevPosition, prevVisitedParent;
do {
prevPosition = this.position;
prevVisitedParent = this._visitedParent;
({ done, value } = this.next());
} while (!done && skip(value));
if (!done) {
this._position = prevPosition;
this._visitedParent = prevVisitedParent;
}
}
/**
* Moves tree walker {@link #position} to provided `position`. Tree walker will
* continue traversing from that position.
*
* Note: in contrary to {@link ~ModelTreeWalker#skip}, this method does not iterate over the nodes along the way.
* It simply sets the current tree walker position to a new one.
* From the performance standpoint, it is better to use {@link ~ModelTreeWalker#jumpTo} rather than {@link ~ModelTreeWalker#skip}.
*
* If the provided position is before the start boundary, the position will be
* set to the start boundary. If the provided position is after the end boundary,
* the position will be set to the end boundary.
* This is done to prevent the treewalker from traversing outside the boundaries.
*
* @param position Position to jump to.
*/
jumpTo(position) {
if (this._boundaryStartParent && position.isBefore(this.boundaries.start)) {
position = this.boundaries.start;
}
else if (this._boundaryEndParent && position.isAfter(this.boundaries.end)) {
position = this.boundaries.end;
}
this._position = position.clone();
this._visitedParent = position.parent;
}
/**
* Gets the next tree walker's value.
*/
next() {
if (this.direction == 'forward') {
return this._next();
}
else {
return this._previous();
}
}
/**
* Makes a step forward in model. Moves the {@link #position} to the next position and returns the encountered value.
*/
_next() {
const previousPosition = this.position;
const position = this.position.clone();
const parent = this._visitedParent;
// We are at the end of the root.
if (parent.parent === null && position.offset === parent.maxOffset) {
return { done: true, value: undefined };
}
// We reached the walker boundary.
if (parent === this._boundaryEndParent && position.offset == this.boundaries.end.offset) {
return { done: true, value: undefined };
}
// Get node just after the current position.
// Use a highly optimized version instead of checking the text node first and then getting the node after. See #6582.
const textNodeAtPosition = getTextNodeAtPosition(position, parent);
const node = textNodeAtPosition || getNodeAfterPosition(position, parent, textNodeAtPosition);
if (node && node.is('model:element')) {
if (!this.shallow) {
// Manual operations on path internals for optimization purposes. Here and in the rest of the method.
position.path.push(0);
this._visitedParent = node;
}
else {
// We are past the walker boundaries.
if (this.boundaries && this.boundaries.end.isBefore(position)) {
return { done: true, value: undefined };
}
position.offset++;
}
this._position = position;
return formatReturnValue('elementStart', node, previousPosition, position, 1);
}
if (node && node.is('model:$text')) {
let charactersCount;
if (this.singleCharacters) {
charactersCount = 1;
}
else {
let offset = node.endOffset;
if (this._boundaryEndParent == parent && this.boundaries.end.offset < offset) {
offset = this.boundaries.end.offset;
}
charactersCount = offset - position.offset;
}
const offsetInTextNode = position.offset - node.startOffset;
const item = new ModelTextProxy(node, offsetInTextNode, charactersCount);
position.offset += charactersCount;
this._position = position;
return formatReturnValue('text', item, previousPosition, position, charactersCount);
}
// `node` is not set, we reached the end of current `parent`.
position.path.pop();
position.offset++;
this._position = position;
this._visitedParent = parent.parent;
if (this.ignoreElementEnd) {
return this._next();
}
return formatReturnValue('elementEnd', parent, previousPosition, position);
}
/**
* Makes a step backward in model. Moves the {@link #position} to the previous position and returns the encountered value.
*/
_previous() {
const previousPosition = this.position;
const position = this.position.clone();
const parent = this._visitedParent;
// We are at the beginning of the root.
if (parent.parent === null && position.offset === 0) {
return { done: true, value: undefined };
}
// We reached the walker boundary.
if (parent == this._boundaryStartParent && position.offset == this.boundaries.start.offset) {
return { done: true, value: undefined };
}
// Get node just before the current position.
// Use a highly optimized version instead of checking the text node first and then getting the node before. See #6582.
const positionParent = position.parent;
const textNodeAtPosition = getTextNodeAtPosition(position, positionParent);
const node = textNodeAtPosition || getNodeBeforePosition(position, positionParent, textNodeAtPosition);
if (node && node.is('model:element')) {
position.offset--;
if (this.shallow) {
this._position = position;
return formatReturnValue('elementStart', node, previousPosition, position, 1);
}
position.path.push(node.maxOffset);
this._position = position;
this._visitedParent = node;
if (this.ignoreElementEnd) {
return this._previous();
}
return formatReturnValue('elementEnd', node, previousPosition, position);
}
if (node && node.is('model:$text')) {
let charactersCount;
if (this.singleCharacters) {
charactersCount = 1;
}
else {
let offset = node.startOffset;
if (this._boundaryStartParent == parent && this.boundaries.start.offset > offset) {
offset = this.boundaries.start.offset;
}
charactersCount = position.offset - offset;
}
const offsetInTextNode = position.offset - node.startOffset;
const item = new ModelTextProxy(node, offsetInTextNode - charactersCount, charactersCount);
position.offset -= charactersCount;
this._position = position;
return formatReturnValue('text', item, previousPosition, position, charactersCount);
}
// `node` is not set, we reached the beginning of current `parent`.
position.path.pop();
this._position = position;
this._visitedParent = parent.parent;
return formatReturnValue('elementStart', parent, previousPosition, position, 1);
}
}
function formatReturnValue(type, item, previousPosition, nextPosition, length) {
return {
done: false,
value: {
type,
item,
previousPosition,
nextPosition,
length
}
};
}