myGlobal.undefined in ECMAScript 262

The static value "undefined"

Property Type

Here are some examples where undefined exists in the language:

As a property of the Global object, the undefined value should be available for comparison. However, some ECMAScript interpretters (such as that used by IE for MacOS) do not include it. An alternative way to compare for undefined (as opposed to null) is to use typeof:

var foo;
if (typeof(foo)=='undefined'){
    // this code will execute; typeof(undefined) is the string 'undefined'