Regex optimizations (#2132)
* Remove regex construction for SimpleDOMParser.getElementsByClassName * Remove regex construction for CssStyleApplier._getRulesForClass * Rename, add jsdoc for clarity
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@ -20,6 +20,14 @@
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* that is the same across different browsers.
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*/
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class CssStyleApplier {
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/**
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* @typedef {object} CssRule
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* @property {string} selectors A CSS selector string representing one or more selectors.
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* @property {[string, string][]} styles A list of CSS property and value pairs.
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* @property {string} styles[][0] The CSS property.
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* @property {string} styles[][1] The CSS value.
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*/
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/**
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* Creates a new instance of the class.
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* @param styleDataUrl The local URL to the JSON file continaing the style rules.
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@ -37,6 +45,9 @@ class CssStyleApplier {
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this._styleDataUrl = styleDataUrl;
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this._styleData = [];
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this._cachedRules = new Map();
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// eslint-disable-next-line no-control-regex
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this._patternHtmlWhitespace = /[\t\r\n\x0C ]+/g;
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this._patternClassNameCharacter = /[0-9a-zA-Z-_]/;
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}
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/**
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@ -65,7 +76,7 @@ class CssStyleApplier {
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const className = element.getAttribute('class');
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if (className.length === 0) { continue; }
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let cssTextNew = '';
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for (const {selectorText, styles} of this._getRulesForClass(className)) {
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for (const {selectorText, styles} of this._getCandidateCssRulesForClass(className)) {
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if (!element.matches(selectorText)) { continue; }
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cssTextNew += this._getCssText(styles);
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}
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@ -99,17 +110,22 @@ class CssStyleApplier {
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return await response.json();
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}
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_getRulesForClass(className) {
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/**
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* Gets an array of candidate CSS rules which might match a specific class.
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* @param {string} className A whitespace-separated list of classes.
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* @returns {CssRule[]} An array of candidate CSS rules.
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*/
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_getCandidateCssRulesForClass(className) {
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let rules = this._cachedRules.get(className);
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if (typeof rules !== 'undefined') { return rules; }
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rules = [];
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this._cachedRules.set(className, rules);
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const classNamePattern = new RegExp(`.${className}(?![0-9a-zA-Z-])`, '');
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const classList = this._getTokens(className);
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for (const {selectors, styles} of this._styleData) {
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const selectorText = selectors.join(',');
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if (!classNamePattern.test(selectorText)) { continue; }
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if (!this._selectorMatches(selectorText, classList)) { continue; }
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rules.push({selectorText, styles});
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}
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@ -123,4 +139,33 @@ class CssStyleApplier {
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}
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return cssText;
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}
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_selectorMatches(selectorText, classList) {
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const pattern = this._patternClassNameCharacter;
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for (const item of classList) {
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const prefixedItem = `.${item}`;
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let start = 0;
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while (true) {
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const index = selectorText.indexOf(prefixedItem, start);
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if (index < 0) { break; }
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start = index + prefixedItem.length;
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if (start >= selectorText.length || !pattern.test(selectorText[start])) { return true; }
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}
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}
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return false;
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}
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_getTokens(tokenListString) {
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let start = 0;
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const pattern = this._patternHtmlWhitespace;
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pattern.lastIndex = 0;
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const result = [];
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while (true) {
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const match = pattern.exec(tokenListString);
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const end = match === null ? tokenListString.length : match.index;
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if (end > start) { result.push(tokenListString.substring(start, end)); }
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if (match === null) { return result; }
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start = end + match[0].length;
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}
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}
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}
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@ -22,6 +22,8 @@
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class SimpleDOMParser {
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constructor(content) {
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this._document = parse5.parse(content);
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// eslint-disable-next-line no-control-regex
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this._patternHtmlWhitespace = /[\t\r\n\x0C ]+/g;
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}
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getElementById(id, root=null) {
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@ -54,11 +56,10 @@ class SimpleDOMParser {
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getElementsByClassName(className, root=null) {
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const results = [];
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const classNamePattern = new RegExp(`(^|\\s)${escapeRegExp(className)}(\\s|$)`);
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for (const node of this._allNodes(root)) {
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if (typeof node.tagName === 'string') {
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const nodeClassName = this.getAttribute(node, 'class');
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if (nodeClassName !== null && classNamePattern.test(nodeClassName)) {
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if (nodeClassName !== null && this._hasToken(nodeClassName, className)) {
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results.push(node);
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}
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}
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@ -114,4 +115,17 @@ class SimpleDOMParser {
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}
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}
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}
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_hasToken(tokenListString, token) {
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let start = 0;
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const pattern = this._patternHtmlWhitespace;
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pattern.lastIndex = 0;
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while (true) {
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const match = pattern.exec(tokenListString);
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const end = match === null ? tokenListString.length : match.index;
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if (end > start && tokenListString.substring(start, end) === token) { return true; }
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if (match === null) { return false; }
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start = end + match[0].length;
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}
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}
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}
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