JavaScript undefined Property

Complete Function Reference

Definition and Usage

Syntax

undefined

Example

In this example we will test two variables to find out if one of them is undefined:

<script type="text/javascript">

var t1="";
var t2;

if (t1==undefined)
{
document.write("t1 is undefined");
}
if (t2==undefined)
{
document.write("t2 is undefined");
}

</script>

The output of the code above will be:

t2 is undefined

Try-It-Yourself Demos

undefined
How to test if a variable is undefined.

Complete Function Reference

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