Standard JavaScript guide

README.md

Standard JavaScript

This is a TL;DR of the standard and semistandard JavaScript rules. For more detailed explanations, see standard's rules documentation.

Rules

• Use 2 spaces for indentation.

  function hello (name) {
    console.log('hi', name)
  }

• Use single quotes for strings except to avoid escaping.

  console.log('hello there')
  $("<div class='box'>")

• No unused variables.

  function myFunction () {
    var result = something()   // ✗ avoid
  }

• Add a space after keywords.

  if (condition) { ... }   // ✓ ok
  if(condition) { ... }    // ✗ avoid

• Add a space after function names.

  function name (arg) { ... }   // ✓ ok
  function name(arg) { ... }    // ✗ avoid
  
  run(function () { ... })      // ✓ ok
  run(function() { ... })       // ✗ avoid

• Always use === instead of ==.
  Exception: obj == null is allowed to check for null || undefined.

  if (name === 'John')   // ✓ ok
  if (name == 'John')    // ✗ avoid
  
  if (name !== 'John')   // ✓ ok
  if (name != 'John')    // ✗ avoid

• Always handle the err function parameter.

  // ✓ ok
  run(function (err) {
    if (err) throw err
    window.alert('done')
  })
  
  // ✗ avoid
  run(function (err) {
    window.alert('done')
  })

• Always prefix browser globals with window..
  Exceptions are: document, console and navigator.

  window.alert('hi')   // ✓ ok

Semicolons

These rules are enforced for standard, but are not imposed in semistandard.

• No semicolons. (see: 1, 2, 3)

  window.alert('hi')   // ✓ ok
  window.alert('hi');  // ✗ avoid

• Never start a line with ( or [. This is the only gotcha with omitting semicolons. (see: 1)

  ;(function () {
    window.alert('ok')
  }())