aneurysmjs

/**
 * match first character after white space
 */
const firstAtWhiteSpace = /(^|\s)[a-z]/g;

aneurysmjs

// in this case the state is each individual product
const product = (state, action) => {
  switch (action.type) {
    case 'CREATE_PRODUCT':
      return {
        id: action.id,
        name: action.name,
        price: action.price,
      };
    case 'EDIT_PRODUCT':

aneurysmjs

<!-- 
  even though the "blue" comes later in the list of classes,
  but CSS rules of precedence actually depends of the order of
  classes in the stylesheet
-->
<span class="red blue">
  so I'm red
</span>

aneurysmjs

/**
 * @link this is taken from here for reference
 * https://github.com/testing-library/react-hooks-testing-library/issues/20#issuecomment-476628600
 */
import { useState, useEffect } from 'react';
import { renderHook } from '@testing-library/react-hooks';

describe('error hook tests', () => {
  function useError(obj: Error | string): boolean {
    if (obj.constructor.name === 'Error') {

aneurysmjs

// .babelrc
{
  "presets": [
    [
      "@babel/preset-env",
      { 
        // this tells @babel "hey, don'y change any of the modules, let Webpack handle it
        "modules": false
         // you only get the individual pollyfill that you need
         "useBuiltIns": "usage"

aneurysmjs

interface Base {
  id: string;
  timestamp: string;
}

interface Product extends Base {
  price: number;
  stock: number;
}

aneurysmjs

const { PerformanceObserver, performance } = require('perf_hooks');

const obs = new PerformanceObserver((items) => {
  console.log(items.getEntries()[0]);
  performance.clearMarks();
});

obs.observe({ entryTypes: ['measure'] });

const has = Object.prototype.hasOwnProperty;

aneurysmjs

const connect = (mapStateToProps) => (Component) => {
  return class Connect extends React.Component {
    state = mapStateToProps(store.getState());
    
    componentDidMount() {
      // когда store меняется, обновит компонент
      this.unsubscribe = store.subscribe(this.update);
    }
    
    componentWillUnmount() {

aneurysmjs

/**
 * understanding .constructor property
 */

function User() {

}

// when functions are created, they're given a "prototype" property which is an object
console.log(User.prototype);  // {}

aneurysmjs

const data = [
    {username: 'bob', age: 30, tags: ['work', 'boring']},
    {username: 'jim', age: 25, tags: ['home', 'fun']},
    {username: 'jane', age: 30, tags: ['vacation', 'fun']}
];

R.filter(R.where({tags: R.contains('fun')}))(data);

const users = [
    {username: 'bob', age: 30, tags: [{label: 'work'}, {label: 'boring'}]},