lahmatiy

const csstree = require("css-tree");
const cssDefinitions = ["color"];
const ast = csstree.parse(`
.some-selector {
  color: black;
  border: 1px solid #fff;
}
`, { parseValue: false });

csstree.walk(ast, {

lahmatiy

const cssTree = require("css-tree@1.0.0-alpha.29");

function getSelectorParent(selector) {
    const selectorAst = cssTree.parse(selector, { context: 'selector' });

    // solution #1
    selectorAst.children.prevUntil(selectorAst.children.tail, (node, item, list) => {
        list.remove(item);
        return node.type === 'Combinator' || node.type === 'WhiteSpace';
    });

lahmatiy

const cssTree = require("css-tree@1.0.0-alpha.29");

function getSelectorParent(selector) {
    const selectorAst = cssTree.parse(selector, { context: 'selector' });
    // solution #1
    // selectorAst.children.prevUntil(selectorAst.children.tail, (node, item, list) => {
    //     list.remove(item);
    //     return node.type === 'Combinator' || node.type === 'WhiteSpace';
    // });
    

lahmatiy

const cssTree = require("css-tree@1.0.0-alpha.29");

function getSelectorParent(selector) {
    const selectorAst = cssTree.parse(selector, { context: 'selector' });
    // solution #1
    // selectorAst.children.prevUntil(selectorAst.children.tail, (node, item, list) => {
    //     list.remove(item);
    //     return node.type === 'Combinator' || node.type === 'WhiteSpace';
    // });
    

lahmatiy

// UPDATE: you can use ready to use package prop-types-definition
// https://github.com/avito-tech/prop-types-definition

module.exports = function(content) {
    return content + `
(function(ReactPropTypes) {
  function unwrapValueItem(value) {
    if (value) {
      if (typeof value.getTypeDefinition === 'function') {
        return value.getTypeDefinition();

lahmatiy

const csstree = require('css-tree');

const ast1 = csstree.parse('.a { color: red }', {
  filename: './a.css',
  positions: true
});
const ast2 = csstree.parse('.b { color: red }', {
  filename: './b.css',
  positions: true
});

lahmatiy

const csstree = require('css-tree');
const data = require('mdn-data/css/properties.json');

Object.keys(data).forEach(name => {
    const prop = data[name];

    if (Array.isArray(prop.initial)) {
        return;
    }

lahmatiy

const pngSignature = Buffer.from([137, 80, 78, 71, 13, 10, 26, 10]);
const hashKey = 'react-snapshot-hash';
const crcTable = [];
const initialCrc = 0xffffffff;

for (let n = 0; n < 256; n++) {
    let c = n;

    for (let k = 0; k < 8; k++) {
        if (c & 1) {

lahmatiy

const EXTENSION_TYPE = {
    0x01: 'PlainText',
    0xF9: 'GraphicControl',
    0xFE: 'Comment',
    0xFF: 'Application'
};

/**
 * Returns total length of data blocks sequence
 *

lahmatiy

Similar solutions with very different execution times. What's the reason? Why solution #1 is too slow?

Hint: access to .length property and to variables is not an issue.

Based on a real case in CSSTree

Node v6.11.3

N	Solution #1	Solution #2