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Get selector optimisation #134

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1 change: 1 addition & 0 deletions lib/core/constants.js
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,7 @@ const definitions = [
const constants = {
helpUrlBase: 'https://dequeuniversity.com/rules/',
gridSize: 200,
selectorSimilarFilterLimit: 700,
results: [],
resultGroups: [],
resultGroupMap: {},
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18 changes: 15 additions & 3 deletions lib/core/utils/get-selector.js
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Expand Up @@ -4,6 +4,8 @@ import getNodeAttributes from './get-node-attributes';
import matchesSelector from './element-matches';
import isXHTML from './is-xhtml';
import getShadowSelector from './get-shadow-selector';
import memoize from './memoize';
import constants from '../../core/constants';

const ignoredAttributes = [
'class',
Expand Down Expand Up @@ -376,8 +378,8 @@ function generateSelector(elm, options, doc) {
} else {
selector = features;
}
if (!similar) {
similar = Array.from(doc.querySelectorAll(selector));
if (!similar || similar.length > constants.selectorSimilarFilterLimit) {
similar = findSimilar(doc, selector);
} else {
similar = similar.filter(item => {
return matchesSelector(item, selector);
Expand All @@ -401,6 +403,16 @@ function generateSelector(elm, options, doc) {
* @param {Object} optional options
* @returns {String|Array<String>} Unique CSS selector for the node
*/
export default function getSelector(elm, options) {
function getSelector(elm, options) {
return getShadowSelector(generateSelector, elm, options);
}

// Axe can call getSelector more than once for the same element because
// the same element can end up on multiple DqElements.
export default memoize(getSelector);

// Similar elements create similar selectors. If there are lots of similar elements on the page,
// axe ends up needing to run that same selector many times. We can memoize for a huge perf boost.
const findSimilar = memoize((doc, selector) =>
Array.from(doc.querySelectorAll(selector))
);
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