JavaScript typeof

We can use typeof function to know about type of variable used. This function tells us that the variable is a string or number or Boolean or any object. Most important is getting the output as 'undefined' which tells us that the variable does not exist. So we can take corrective action.

Here are some examples.
<script type="text/javascript">
function my_fun(){

}
var v1= new my_fun();
document.write(typeof(v1) + "<br>"); // output is object

var v2= "plus2net";
document.write(typeof(v2) + "<br>"); // output is string

var v3= 5.73;
document.write(typeof(v3) + "<br>"); // output is number

var v4= 18
document.write(typeof(v4) + "<br>"); // output is number

var students= new Array;
document.write(typeof(students) + "<br>"); // output is object

var v5 = false;
document.write(typeof(v5) + "<br>"); // output is boolean


document.write(typeof(v6) + "<br>"); // output is undefined

</script>
We will use typeof() after converting a string variable to number by using parseFloat
var v1 = "5.25";
document.write(typeof(v1) + "<br>"); // output is  string

v1=parseFloat(v1);
document.write(typeof(v1) + "<br>"); // output is number


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