Check if a value is undefined in JavaScript
Description
The following code shows how to check if a value is undefined.
Example
<!--from w w w . j a v a 2 s . c o m-->
<!DOCTYPE html>
<html>
<head>
<script type="text/javascript">
var aString;
document.writeln(aString == undefined);
</script>
</head>
<body>
</body>
</html>
The code above generates the following result.
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Find out the difference between undefined v...
Treat undefined the same as null, you can u...
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