slikts

Advanced memoization and effects in React

Memoization is a somewhat fraught topic in the React world, meaning that it's easy to go wrong with it, for example, by [making memo() do nothing][memo-pitfall] by passing in children to a component. The general advice is to avoid memoization until the profiler tells you to optimize, but not all use cases are general, and even in the general use case you can find tricky nuances.

Discussing this topic requires some groundwork about the technical terms, and I'm placing these in once place so that it's easy to skim and skip over:

• Memoization means caching the output based on the input; in the case of functions, it means caching the return value based on the arguments.
• Values and references are unfortunately overloaded terms that can refer to the low-level implementation details of assignments in a language like C++, for example, or to memory

tomhicks

/*
Copy this into the console of any web page that is interactive and doesn't
do hard reloads. You will hear your DOM changes as different pitches of
audio.

I have found this interesting for debugging, but also fun to hear web pages
render like UIs do in movies.
*/

const audioCtx = new (window.AudioContext || window.webkitAudioContext)()

m4n1ok

export const isAutoplaySupported = () => {
  // Detect if user can autoplay inline video
  // Works when user is on low-battery mode on IOS
  // Return promise from video.play
  const video = document.createElement('video')
  video.src = 'data:video/mp4;base64,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

adamwathan

// Creates a new promise that automatically resolves after some timeout:
Promise.delay = function (time) {
    return new Promise((resolve, reject) => {
        setTimeout(resolve, time)
    })
}

// Throttle this promise to resolve no faster than the specified time:
Promise.prototype.takeAtLeast = function (time) {
    return new Promise((resolve, reject) => {

sAbakumoff

• nylas/N1 💌 An extensible desktop mail app built on the modern web.
• black-screen/black-screen A terminal emulator for the 21st century.
• shockone/black-screen A terminal emulator for the 21st century.
• ptmt/react-native-macos React Native for macOS
• docker/kitematic Visual Docker Container Management on Mac & Windows
• kitematic/kitematic Visual Docker Container Management on Mac & Windows
• davezuko/wirk-starter Get started with React, Redux, and React-Router!
• TelescopeJS/Telescope 🔭 An open-source social news app built with Meteor & React
• coryhouse/react-slingshot React + Redux starter kit / boile

pangeaware

var React = require('react');

var LinkedinLogin = React.createClass({

    componentDidMount: function() {
        var liRoot = document.createElement('div');
        liRoot.id = 'linkedin-root';

        document.body.appendChild(liRoot);

fay-jai

import React from "react";
import { render } from "react-dom";

const ParentComponent = React.createClass({
  getDefaultProps: function() {
    console.log("ParentComponent - getDefaultProps");
  },
  getInitialState: function() {
    console.log("ParentComponent - getInitialState");
    return { text: "" };

ctlcltd

How to easily generate low quality image placeholders (lqip) in WordPress

I have made this function using the WP_Image_Editor class and I have filtered through the "wp_generate_attachment_metadata" hook. You can modify the "theme" namespace into function names with your theme name or in anyway you like.

Applying the filter directly to wp_generate_attachment_metadata the image placeholders are auto added into WordPress metadata, so when your add/modify/delete an image (or regenerate it via a plugin), it accomplishes to modify also to the image placeholders.

The use of the native theme support can prevent the generation of lqip or target specific image sizes to generate.

It contains an hook filter lqip_quality to modify the quality without have to modify the function.

wesbos

{
  "keys": ["tab"], 
  "command": "expand_abbreviation_by_tab", 

  // put comma-separated syntax selectors for which 
  // you want to expandEmmet abbreviations into "operand" key 
  // instead of SCOPE_SELECTOR.
  // Examples: source.js, text.html - source
  "context": [
    {

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