JS & DOM Reference
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JavaScript undefined Property
JavaScript Global Functions
Definition and Usage
The undefined property indicates that a variable has not been assigned a value.
Browser Support
The undefined property is supported in all major browsers.
Example
Example
Test if variables are 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>
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 »
JavaScript Global Functions
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Tutorials, references, and examples are constantly reviewed to avoid errors, but we cannot warrant full correctness of all content.
While using this site, you agree to have read and accepted our terms of use and privacy policy.
Copyright 1999-2012 by Refsnes Data. All Rights Reserved.
Tutorials, references, and examples are constantly reviewed to avoid errors, but we cannot warrant full correctness of all content.
While using this site, you agree to have read and accepted our terms of use and privacy policy.
Copyright 1999-2012 by Refsnes Data. All Rights Reserved.