selectors.js•3.35 kB
import { AttributeAction, SelectorType, isTraversal as isTraversalBase, } from "css-what";
export function isTraversal(token) {
return token.type === "_flexibleDescendant" || isTraversalBase(token);
}
/**
* Sort the parts of the passed selector, as there is potential for
* optimization (some types of selectors are faster than others).
*
* @param arr Selector to sort
*/
export function sortRules(arr) {
const ratings = arr.map(getQuality);
for (let i = 1; i < arr.length; i++) {
const procNew = ratings[i];
if (procNew < 0)
continue;
// Use insertion sort to move the token to the correct position.
for (let j = i; j > 0 && procNew < ratings[j - 1]; j--) {
const token = arr[j];
arr[j] = arr[j - 1];
arr[j - 1] = token;
ratings[j] = ratings[j - 1];
ratings[j - 1] = procNew;
}
}
}
function getAttributeQuality(token) {
switch (token.action) {
case AttributeAction.Exists: {
return 10;
}
case AttributeAction.Equals: {
// Prefer ID selectors (eg. #ID)
return token.name === "id" ? 9 : 8;
}
case AttributeAction.Not: {
return 7;
}
case AttributeAction.Start: {
return 6;
}
case AttributeAction.End: {
return 6;
}
case AttributeAction.Any: {
return 5;
}
case AttributeAction.Hyphen: {
return 4;
}
case AttributeAction.Element: {
return 3;
}
}
}
/**
* Determine the quality of the passed token. The higher the number, the
* faster the token is to execute.
*
* @param token Token to get the quality of.
* @returns The token's quality.
*/
export function getQuality(token) {
// eslint-disable-next-line @typescript-eslint/switch-exhaustiveness-check
switch (token.type) {
case SelectorType.Universal: {
return 50;
}
case SelectorType.Tag: {
return 30;
}
case SelectorType.Attribute: {
return Math.floor(getAttributeQuality(token) /
// `ignoreCase` adds some overhead, half the result if applicable.
(token.ignoreCase ? 2 : 1));
}
case SelectorType.Pseudo: {
return !token.data
? 3
: token.name === "has" ||
token.name === "contains" ||
token.name === "icontains"
? // Expensive in any case — run as late as possible.
0
: Array.isArray(token.data)
? // Eg. `:is`, `:not`
Math.max(
// If we have traversals, try to avoid executing this selector
0, Math.min(...token.data.map((d) => Math.min(...d.map(getQuality)))))
: 2;
}
default: {
return -1;
}
}
}
export function includesScopePseudo(t) {
return (t.type === SelectorType.Pseudo &&
(t.name === "scope" ||
(Array.isArray(t.data) &&
t.data.some((data) => data.some(includesScopePseudo)))));
}
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