How To Null Check In Javascript

In JavaScript, null is an assignment value that represents no value or no object. It is often used to indicate that a variable should not have any value or object. In this blog post, we will discuss how to perform a null check in JavaScript and examine some common coding patterns for handling null values.

Basic Null Check

The simplest way to check if a variable is null is to use the strict equality operator (===) to compare the variable with null. Here’s an example:

const variable = null;

if (variable === null) {
    console.log('The variable is null.');
} else {
    console.log('The variable is not null.');
}

Checking for Null or Undefined

In JavaScript, undefined is another special value that represents the absence of a value. If a variable has not been assigned a value, its value is undefined. In many cases, you might want to check for both null and undefined when performing a null check.

You can use the loose equality operator (==) to check if a variable is either null or undefined:

const variable;

if (variable == null) {
    console.log('The variable is either null or undefined.');
} else {
    console.log('The variable has a value.');
}

Alternatively, you can use the typeof operator to check if a variable is undefined:

const variable;

if (variable === null || typeof variable === 'undefined') {
    console.log('The variable is either null or undefined.');
} else {
    console.log('The variable has a value.');
}

Truthy and Falsy Values

JavaScript has a concept of truthy and falsy values. A value is considered truthy if it evaluates to true in a boolean context, and falsy if it evaluates to false. Both null and undefined are considered falsy values, along with false, 0, NaN, and the empty string ”.

To check if a variable is truthy, you can use the following conditional statement:

const variable = null;

if (variable) {
    console.log('The variable is truthy.');
} else {
    console.log('The variable is falsy.');
}

This method can be useful for null checks in some situations, but be aware that it also considers other falsy values like false, 0, and ” as “null”. If you only want to check for null and undefined specifically, use the methods mentioned in the previous section.

Conclusion

In this blog post, we’ve covered different ways to perform a null check in JavaScript. Remember to use the appropriate method depending on whether you need to check for null specifically, or both null and undefined, and be mindful of the difference between truthy and falsy values.