| 5. 9. 1. Undefined Values |
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The variable is 'undefined' if no value has been assigned to it. |
Undefined number value is NaN. |
Undefined string value is 'undefined'. |
Undefined boolean value is false. |
The undefined property is a primitive value of the global object. |
undefined is returned by variables that have not had values assigned to them. |
undefined is also returned by methods if the variable being evaluated is not assigned a value. |
The following example tests a Variable to See if It is Undefined. |
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<html>
<script language="JavaScript1.3">
<!--
var myVariable;
if(myVariable == undefined){
document.write("This variable is undefined at the moment");
}else{
document.write("This variables value is: " + myVariable);
}
-->
</script>
</html>
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