garybernhardt

This document has moved!

It's now here, in The Programmer's Compendium. The content is the same as before, but being part of the compendium means that it's actively maintained.

mathiasbynens

Looking for support tables for HTML/CSS/JavaScript features or details on their implementation status in major browsers?

• Chrome Platform Status (covers Chromium and thus includes Opera)
• Firefox Platform Status
• Microsoft Edge Platform Status
• WebKit Feature Status
• API Catalog

And then there’s Can I use…?.

gaearon

function mapValues(obj, fn) {
  return Object.keys(obj).reduce((result, key) => {
    result[key] = fn(obj[key], key);
    return result;
  }, {});
}

function pick(obj, fn) {
  return Object.keys(obj).reduce((result, key) => {
    if (fn(obj[key])) {

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

jquense

import { createStore } from 'redux';
import combineReducers from './combineReducers';

let Store = createStore(combineReducers({
  
  reducerA(state = 0, action, waitFor){
    if ( action.type === 'TEST'){
      waitState = waitFor(waitFor.reducerB)
      if ( waitState.reducerB === 5 )
        state = 10

pjdietz

function rfc3339(d) {
    
    function pad(n) {
        return n < 10 ? "0" + n : n;
    }

    function timezoneOffset(offset) {
        var sign;
        if (offset === 0) {
            return "Z";

imjasonh

* {
    font-size: 12pt;
    font-family: monospace;
    font-weight: normal;
    font-style: normal;
    text-decoration: none;
    color: black;
    cursor: default;
}

p3t3r67x0

Styling native elements

Native HTML controls are a challenge to style. You can style any element in the web platform that uses Shadow DOM with a pseudo element ::pseudo-element or the /deep/ path selector.

video::webkit-media-controls-timeline {
  background-color: lime;
}

video /deep/ input[type=range] {

addyosmani

CSS Layout Debugger

A tweet-sized debugger for visualizing your CSS layouts. Outlines every DOM element on your page a random (valid) CSS hex color.

One-line version to paste in your DevTools

Use $$ if your browser aliases it:

~ 108 byte version

hdragomir

<script type="text/javascript">
    (function () {
      "use strict";
      // once cached, the css file is stored on the client forever unless
      // the URL below is changed. Any change will invalidate the cache
      var css_href = './index_files/web-fonts.css';
      // a simple event handler wrapper
      function on(el, ev, callback) {
        if (el.addEventListener) {
          el.addEventListener(ev, callback, false);