JavaScript Common Pitfalls

This is a short list of common pitfalls in JavaScript, and some simple solutions for them. A lot of these problems arise from the deeply asynchronous nature of the language and may be applicable to other similar environments. Others are unique to JavaScript's attempts to be beginner friendly, and attempting to do something sensible given ambiguous input. Example code is also on GitHub here .

Loops and asynchronous operations

Events aren't always asynchronous

Deeply nested callbacks for serial execution

Mysteriously mutating objects

Array like objects

Hoisting

Block statements

Arrow function returns

Circular dependencies

Falsey 0

Node EventEmitter error events

Object Equality

Properties on window are global variables

Recursion Depth

eval vrs. new Function

binding `this`

Insignificantish whitespace

parallel execution

Nested branching

Get the full result of a stream

Type casting

Object iteration

Node style callback

Asynchronous Loops

Finding the global object

Accuracy of the Date object

Timer durations

Timer Precedence

Reduce