How to unset a JavaScript variable?
By Saruque Ahamed MollickIn this JavaScript tutorial, I will explain if you can delete a variable or not in JavaScript. If yes, then how you can delete a variable or unset a JavaScript variable easily.
Someone says it delete someone says unset.
Delete is an operator by Which you can remove a property of an object. But it can’t be used to delete a variable.
So it is clear, you can’t delete a property which is created with var by using delete operator. But you can delete a property ( or a variable whatever you say ) which is created without var.
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Unset a JavaScript Variable or Delete a JavaScript Variable
Just look at these two examples I am gonna provide below.
<!DOCTYPE html>
<html>
<head>
<title>Title goes here</title>
</head>
<body>
<script type="text/javascript">
var some_variable= 23;
delete some_variable;
document.write(some_variable);
</script>
</body>
</html>
Output:
23
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What happened?
<script type="text/javascript"> var some_variable= 23; // used var here delete some_variable; // it will return false document.write(some_variable); // value of some_variable will be still here </script>
Now see the second example. This time we gonna create a variable without var
<!DOCTYPE html>
<html>
<head>
<title>Title goes here</title>
</head>
<body>
<script type="text/javascript">
some_variable= 23;
delete some_variable;
document.write(some_variable);
</script>
</body>
</html>
Output:
So, you will get a blank output. Because now the property some_variable is gone.
( In the earlier versions of browsers It can be show you as some_variable is not defined, but now it will not show you any error. Instead of any kind of error it will show nothing )
Why?
<script type="text/javascript"> some_variable= 23; // now this is a property not a variable delete some_variable; // this will return true document.write(some_variable); // will show you the value of some_variable </script>
Special Note:
Finally, You can also use
some_variable= undefined;; // unset variable
It will unset the variable.
Moreover, You may also be interested in,
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