caniuse

Support tables for HTML5, CSS3, etc 

regex101

RegExp Online Testing 

JSON Editor Online

Front End JSON Editor 

Test My Site

Test how mobile-friendly your site is 

JSON formatter

JSON formatter 

Jade Converter

html to Pug/Jade 

CodePad

online coding interview 

reveal.js

presentations using HTML 

pypi ranking

Hackerrank

online test 

Crontab guru

ColorPK

By ZJ Guo 

Palettab

Discover new discover fonts and colors 

ColourCode

find color scheme 

Coolors

find cool colors 

UI Gradients

colored gradient 

JavaScript秘密花园

Javascript入门文档 

React + Webpack

Gitbook 英文原版 

ES6 入门

阮一峰：开源的 JavaScript 语言教程 

JS Tips

Javascript tips everyday 

W3Schools

Web Dev tutorial 

React.js小书

胡子大哈 

廖雪峰JS教程

blog, tutorial and QA 

Modern Javascript

tutorial 

re-intro to JS

MDN Tutorial 

前端九部

支付宝内部资料 

GraphQL

principle 

Eloquent

javascript 

git-branch

learning 

StandardJS

Javascript Standard Style 

airbnb JavaScript

airbnb javascript style guide 

Vanilla JS

You may not need jQuery 

Code For Geek

Programming blog 

Richard Clayton

Unrepentant Thoughts on code 

积木村の研究所

foio 

yuguo

Coding Horror

Jeff Atwood!!! 

海底苍鹰

Tank 

Angular in depth

advanced rxjs 

Hackages Blog

home for js & web 

Addy Osmani

design pattern 

Addy Osmani

Dan Abramov

best of JS

github feature package 

javascripting

database for js source 

State of JS

TestMySite

Mobile Speed By Google 

Lighthouse

By Google 

Sitespeed.io

Measuring performance 

Global Latency

speed test 

Bundlephobia

bundle package size 

Convertio

SVGO

Disqus

comment bar 

Intercom

online messaging 

Webix

snky

Rico's

CodePen

Online Front End Playground 

JS Bin

Collaborative JavaScript Debugging 

Liveweave

online JS 

Plunker

online web development 

CSS Deck

online css portfolio 

JSFiddle

JavaScript Fiddle with boilerplate 

CodeSandbox

Powerful online code editor 

StackBlitz