RULES.md

JavaScript Happiness Style

This is a TL;DR of the happiness JavaScript rules.

The best way to learn about happiness is to just install it and give it a try on your code.

Rules

• Use tabs 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 before a function declaration's parentheses.

  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

• Infix operators must be spaced.

  // ✓ ok
  var x = 2
  var message = 'hello, ' + name + '!'

  // ✗ avoid
  var x=2
  var message = 'hello, '+name+'!'

• Commas should have a space after them.

  // ✓ ok
  var list = [1, 2, 3, 4]
  function greet (name, options) { ... }

  // ✗ avoid
  var list = [1,2,3,4]
  function greet (name,options) { ... }

• Keep else statements on the same line as their curly braces.

  // ✓ ok
  if (condition) {
    // ...
  } else {
    // ...
  }

  // ✗ avoid
  if (condition) {
    // ...
  }
  else {
    // ...
  }

• For multi-line if statements, use curly braces.

  // ✓ ok
  if (options.quiet !== true) console.log('done')

  // ✓ ok
  if (options.quiet !== true) {
    console.log('done')
  }

  // ✗ avoid
  if (options.quiet !== true)
    console.log('done')

• 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

• Multiple blank lines not allowed.

  // ✓ ok
  var value = 'hello world'
  console.log(value)

  // ✗ avoid
  var value = 'hello world'
  
  
  console.log(value)

• For the ternary operator in a multi-line setting, place ? and : on their own lines.

  // ✓ ok
  var location = env.development ? 'localhost' : 'www.api.com'
  
  // ✓ ok
  var location = env.development
    ? 'localhost'
    : 'www.api.com'
  
  // ✗ avoid
  var location = env.development ?
    'localhost' :
    'www.api.com'

• For var declarations, write each declaration in its own statement.

  // ✓ ok
  var silent = true
  var verbose = true
  
  // ✗ avoid
  var silent = true, verbose = true
  
  // ✗ avoid
  var silent = true,
      verbose = true

• Wrap conditional assignments with additional parentheses. This makes it clear that the expression is intentionally an assignment (=) rather than a typo for equality (===).

  // ✓ ok
  while ((m = text.match(expr))) {
    // ...
  }
  
  // ✗ avoid
  while (m = text.match(expr)) {
    // ...
  }

Semicolons

• Always use semicolons.

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