JavaScript

Style

• Use camelCase with a leading lowercase for variables, methods, and object properties.
• Use CamelCase with a leading uppercase for classes.
• Use SCREAMING_SNAKE_CASE for constants.
  • Never use const - it’s not supported in IE.
• ALWAYS use semi-colons.
• ALWAYS use curly-braces when starting/ending blocks and functions. Start the curly brace on the same line as the block and end on a new line.
• Use whitespace to break code in logical paragraphs.
• Prefer single quotes ' for strings.

Functions

• Nested functions are okay; but
• DO NOT declare functions within blocks:

  // bad
  if (x) {
    function foo() {};
  }

  // good
  if (x) {
    var foo = function() {};
  }

Other

• Avoid using eval(). This can be very dangerous and can usually be avoided.
• Do not use a for..in loop UNLESS iterating over a hash. It’s best to use the standard for loop in most cases.
• BE CONSISTENT.