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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
/**
* This is a utility object to work with HTML labels in web pages,
* including finding label elements and label text extraction.
*/
export const LabelUtils = {
// The tag name list is from Chromium except for "STYLE":
// eslint-disable-next-line max-len
EXCLUDED_TAGS: ["SCRIPT", "NOSCRIPT", "OPTION", "STYLE"],
// A map object, whose keys are the id's of form fields and each value is an
// array consisting of label elements correponding to the id.
// @type {Map<string, array>}
_mappedLabels: null,
// An array consisting of label elements whose correponding form field doesn't
// have an id attribute.
// @type {Array<[HTMLLabelElement, HTMLElement]>}
_unmappedLabelControls: null,
// A weak map consisting of label element and extracted strings pairs.
// @type {WeakMap<HTMLLabelElement, array>}
_labelStrings: null,
/**
* Extract all strings of an element's children to an array.
* "element.textContent" is a string which is merged of all children nodes,
* and this function provides an array of the strings contains in an element.
*
* @param {object} element
* A DOM element to be extracted.
* @returns {Array}
* All strings in an element.
*/
extractLabelStrings(element) {
if (this._labelStrings.has(element)) {
return this._labelStrings.get(element);
}
let strings = [];
let _extractLabelStrings = el => {
if (this.EXCLUDED_TAGS.includes(el.tagName)) {
return;
}
if (el.nodeType == el.TEXT_NODE || !el.childNodes.length) {
let trimmedText = el.textContent.trim();
if (trimmedText) {
strings.push(trimmedText);
}
return;
}
for (let node of el.childNodes) {
let nodeType = node.nodeType;
if (nodeType != node.ELEMENT_NODE && nodeType != node.TEXT_NODE) {
continue;
}
_extractLabelStrings(node);
}
};
_extractLabelStrings(element);
this._labelStrings.set(element, strings);
return strings;
},
generateLabelMap(doc) {
this._mappedLabels = new Map();
this._unmappedLabelControls = [];
this._labelStrings = new WeakMap();
for (let label of doc.querySelectorAll("label")) {
let id = label.htmlFor;
let control;
if (!id) {
control = label.control;
if (!control) {
continue;
}
id = control.id;
}
if (id) {
let labels = this._mappedLabels.get(id);
if (labels) {
labels.push(label);
} else {
this._mappedLabels.set(id, [label]);
}
} else {
// control must be non-empty here
this._unmappedLabelControls.push({ label, control });
}
}
},
clearLabelMap() {
this._mappedLabels = null;
this._unmappedLabelControls = null;
this._labelStrings = null;
},
findLabelElements(element) {
if (!this._mappedLabels) {
this.generateLabelMap(element.ownerDocument);
}
let id = element.id;
if (!id) {
return this._unmappedLabelControls
.filter(lc => lc.control == element)
.map(lc => lc.label);
}
return this._mappedLabels.get(id) || [];
},
};
export default LabelUtils;