how to check for datatype in node js- specifically for integer


I tried the following to check for the datatype (specifically for integer), but not working.

var i = "5";

if(Number(i) = 'NaN')
 console.log('This is not number'));

This question is tagged with javascript node.js

~ Asked on 2013-09-27 10:27:46

The Best Answer is


I think of two ways to test for the type of a value:

Method 1:

You can use the isNaN javascript method, which determines if a value is NaN or not. But because in your case you are testing a numerical value converted to string, Javascript is trying to guess the type of the value and converts it to the number 5 which is not NaN. That's why if you console.log out the result, you will be surprised that the code:

if (isNaN(i)) {
    console.log('This is not number');

will not return anything. For this reason a better alternative would be the method 2.

Method 2:

You may use javascript typeof method to test the type of a variable or value

if (typeof i != "number") {
    console.log('This is not number');

Notice that i'm using double equal operator, because in this case the type of the value is a string but Javascript internally will convert to Number.

A more robust method to force the value to numerical type is to use Number.isNaN which is part of new Ecmascript 6 (Harmony) proposal, hence not widespread and fully supported by different vendors.

~ Answered on 2013-09-27 11:02:18


i have used it in this way and its working fine

quantity=prompt("Please enter the quantity","1");
if (!isNaN( quantity ))

return totalAmount;

~ Answered on 2013-09-27 10:39:27

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