Javascript Gotchas

Function Constructor

Function constructor can be invoked without using ()

instanceof Does not Work On Primitive Values

The typeof Operator Is Limited and Buggy

Boolean Object Wrappers Are Always true

Boolean can be called as a function to cast a value to a Boolean

Calling Primitive Wrapper Constructors Without new Returns Primitive Values

Object() Can Produce Primitive Object Wrappers

Accessing Properties On Primitive Values Fails

delete Won't Delete Inherited Properties

Array.length Can Be Set, And Has Side Effects


Rouben Meschian