javascript Type Detection

Type Detection

Since JavaScript is a loosely-typed language, it is sometimes necessary to examine a value to determine its type. (This is sometimes necessary in strongly typed languages as well.) JavaScript provides a typeof operator to facilitate this, but typeof has problems.
Object 'object'
Array 'object'
Function 'function'
String 'string'
Number 'number'
Boolean 'boolean'
null 'object'
undefined 'undefined'

typeof [] produces 'object' instead of 'array'. That isn't totally wrong since arrays in JavaScript inherit from objects, but it isn't very useful. typeof null produces 'object' instead of 'null'. That is totally wrong.

We can correct this by defining our own typeOf function, which we can use in place of the defective typeof operator.