How to Check if a Variable Is Not Null in JavaScript?

There are multiple scenarios where you would generally want to look for the null variable because it can and will crash your whole application. Now that is something that we don’t want to happen. In JavaScript, you can easily check for a null variable with the help of a basic if-else statement. This article will demonstrate this with the help of examples.

Note: Most people confuse null variables with undefined and empty variables for being the same.

Example 1: Checking for Null variable with if – else statement

Simply start by creating a variable and setting its value equal to the keyword null with the following line:

var x = null;

Create another variable with some value in it with the help of the following line:

var y = "Some value";

After that, we are going to create a function that will check variables for a null variable:

function checkNull(ourVar) {
  if (ourVar !== null) {
    console.log("Not a Null variable");
  } else {
    console.log("Null variables Detected");

This function simply uses an if-else statement. After that, we are going to pass both our variables one by one to the function checkNull():


Executing this program will provide us with the following result:

The first line in the output is for the variable “x” and from the output we can determine that it is a null variable.

The second line is for the variable “y”; from the output, we can determine that it is not a null variable.

Example 2: Checking for other falsy values

The null value is known as a falsy value in JavaScript, and there are other falsy values in JavaScript. These falsy values include:

    • NaN
    • “” (an empty string)
    • undefined
    • false
    • And a few more.

However, they cannot be detected as null, and thus if-else statements cannot determine these variables as null.

To demonstrate this, create a few variables with these falsy values with the following lines of code:

var a = undefined;
var b = "";
var c = NaN;
var d = false;
var e = 0;

After that, simply pass these variables one by one to the checkNull() function that we created in the previous example:


Executing the code will give the following output on the terminal:

All of these variables were considered to be non-null even though all belong to the same family which is “falsy values”.


In JavaScript, if-else statements can be used to determine whether a variable is a null variable or not. For this, we simply set the condition inside the if-else statement as (varName !== null), where varName is the variable identifier, we are checking. In this article, we created a function named checkNull() that determines whether the variable passed inside its argument is a null variable or not.

About the author

Abdul Mannan

I am curious about technology and writing and exploring it is my passion. I am interested in learning new skills and improving my knowledge and I hold a bachelor's degree in computer science.