Syntax
delete property
The delete operator deletes properties from objects and array elements from arrays by making them undefined.
Some objects, such as variables created by the var statement, are not affected by the delete operator.
<html>
<script language="JavaScript">
<!--
theDate = new Date();
document.write("theDate=",theDate,"<br>Deleting theDate!<br>");
delete theDate;
document.write("theDate=",theDate); //theDate is undefined
-->
</script>
</html>