craigtaub

// Engine
const React = {
  index: 0,
  state: [],
  useEffect: (callback, dependencies) => {
    const cachedIndex = React.index;
    const hasChanged = dependencies !== React.state[cachedIndex];
    if (dependencies === undefined || hasChanged) {
      callback();

abhinavnigam2207

Function.prototype.myBind = function(...boundArgs) {
    let func = this;
    let context = boundArgs.shift();
    
    if (typeof this !== "function") {
        throw new Error(this + "cannot be bound as it's not callable");
    }

    return function(...targetArgs) {
        func.apply(context, args.concat(targetArgs));

bvaughn

This API was removed in React 17

---

Interaction tracing with React

React recently introduced an experimental profiler API. After discussing this API with several teams at Facebook, one common piece of feedback was that the performance information would be more useful if it could be associated with the events that caused the application to render (e.g. button click, XHR response). Tracing these events (or "interactions") would enable more powerful tooling to be built around the timing information, capable of answering questions like "What caused this really slow commit?" or "How long does it typically take for this interaction to update the DOM?".

With version 16.4.3, React added experimental support for this tracing by way of a new NPM package, scheduler. However the public API for this package is not yet finalized and will likely change with upcoming minor releases, so it should be used with caution.

ebidel

Moved to https://github.com/ebidel/puppeteer-examples

deenjohn

15 - Shallow vs Deep Merge 3

A Pen by deenJohn on CodePen.

License.

WaldoJeffers

const compose = (...fns) => fns.reduce((f, g) => (...args) => f(g(...args)))

// Usage : compose functions right to left
// compose(minus8, add10, multiply10)(4) === 42
//
// The resulting function can accept as many arguments as the first function does
// compose(add2, multiply)(4, 10) === 42

g0t4

• Shortened URL for this gist: https://git.io/v68XM

• GitHub repository: ES6 in Motion

• Arrow Functions

  • Arrow Functions - Mystery - CodePen
    • Completed
  • Arrow Functions - Orders - CodePen
    • Completed

• Arrow Functions - What's wrong with this? - CodePen

btroncone

RxJS 5 Operators By Example

⚠️ UPDATE: I have moved the contents of this gist plus more to http://www.learnrxjs.io and https://github.com/btroncone/learn-rxjs. For expanded examples, explanations, and resources, please check out this new location!

A complete list of RxJS 5 operators with easy to understand explanations and runnable examples.

Table of Contents

• buffer
• bufferCount
• bufferTime

paulirish

What forces layout / reflow

All of the below properties or methods, when requested/called in JavaScript, will trigger the browser to synchronously calculate the style and layout*. This is also called reflow or layout thrashing, and is common performance bottleneck.

Generally, all APIs that synchronously provide layout metrics will trigger forced reflow / layout. Read on for additional cases and details.

Element APIs

Getting box metrics

• elem.offsetLeft, elem.offsetTop, elem.offsetWidth, elem.offsetHeight, elem.offsetParent

sebmarkbage

import { Component } from "React";

export var Enhance = ComposedComponent => class extends Component {
  constructor() {
    this.state = { data: null };
  }
  componentDidMount() {
    this.setState({ data: 'Hello' });
  }
  render() {