snapwich

let _ = global._ = require("lodash");
let Benchmark = global.Benchmark = require("benchmark");
let Promise = require("bluebird");

let { Map } = require("immutable");
let { produce } = require("immer");

function getItems(count) {
  let id = 1;

bvaughn

React recently introduced an experimental profiler API. This page gives instructions on how to use this API in a production release of your app.

Table of Contents

• Profiling in production
  • Create React App
  • Webpack 4

Profiling in production

React DOM automatically supports profiling in development mode for v16.5+, but since profiling adds some small additional overhead it is opt-in for production mode. This gist explains how to opt-in.

bengourley

//
// This program reads a sourcemap from stdin
// and replaces the "mappings" property with
// human readable content. It writes the output
// to stdout.
// 
// 1. install the dependencies:
//    npm i concat-stream vlq
//
// 2. optional: install jq for pretty printing json

sebmarkbage

let cache = new Map();
let pending = new Map();

function fetchTextSync(url) {
  if (cache.has(url)) {
    return cache.get(url);
  }
  if (pending.has(url)) {
    throw pending.get(url);
  }

radum

Articles

Performance API

// https://github.com/WICG/paint-timing
performance.getEntries();
performance.getEntriesByType('paint');

// Calculate the time it spends to run something

drakkein

import { Directive, ElementRef, OnDestroy, OnInit, Renderer2 } from '@angular/core';

@Directive({
  selector: '[iframeResize]',
})
export class IframeResizeDirective implements OnInit, OnDestroy {
  private listener: () => void;
  private observer: MutationObserver;

  get element() {

parshap

Running Node Modules in React Native

How to use packages that depend on Node.js core modules in React Native.

See the [node-libs-react-native][node-libs-react-native] library as a convenience for implementing this method.

Node.js Core Modules

JoeyBurzynski

var str = 'class ಠ_ಠ extends Array {constructor(j = "a", ...c) {const q = (({u: e}) => {return { [`s${c}`]: Symbol(j) };})({});super(j, q, ...c);}}' + 
          'new Promise((f) => {const a = function* (){return "\u{20BB7}".match(/./u)[0].length === 2 || true;};for (let vre of a()) {' +
          'const [uw, as, he, re] = [new Set(), new WeakSet(), new Map(), new WeakMap()];break;}f(new Proxy({}, {get: (han, h) => h in han ? han[h] ' + 
          ': "42".repeat(0o10)}));}).then(bi => new ಠ_ಠ(bi.rd));';

try {
  eval(str);
} catch(e) {
  alert('Your browser does not support ES6!')

davidgilbertson

const results = { undefined: 'your function returned nothing' };
const funcThatReturnsNothing = () => {};
const result = funcThatReturnsNothing();
results[result] === 'your function returned nothing'; // true

davidgilbertson

@mixin for-phone-only {
  @media (max-width: 599px) { @content; }
}
@mixin for-tablet-portrait-up {
  @media (min-width: 600px) { @content; }
}
@mixin for-tablet-landscape-up {
  @media (min-width: 900px) { @content; }
}
@mixin for-desktop-up {