Scripter Javascript Tutorial

20 null and undefined

MDN:

• Standard Built-in Objects: null

• Standard Built-in Objects: undefined

Null and undefined are special values. Null means that a variable is empty, or that the value is unknown at the time. Undefined also means a variable does not have any value, but any variable which is declared but not assigned a value is automatically assigned undefined.

var pitch = null; // explicitly assigned null as its value
var note; // undefined