How to Check for an Empty String in JavaScript

1. Use the === Operator to Check if the String Is Empty in JavaScript
2. Use the length Property to Check if the String Is Empty in JavaScript
3. Convert the Variable to Boolean to Check if the String Is Empty in JavaScript

This tutorial will introduce how to check if the string is empty. Every method will have a code example, which you can run on your machine.

Use the === Operator to Check if the String Is Empty in JavaScript

We can use the strict equality operator (===) to check whether a string is empty or not. The comparison data==="" will only return true if the data type of the value is a string, and it is also empty; otherwise, return false.

Example:

console.log(false === '')
console.log(undefined === '')
console.log(2 === '')
console.log(null === '')
console.log('Hello World!' === '')
console.log('' === '')

Output:

false
false
false
false 
false
true

Example:

var str1 = ''
var str2 = 0
var str3 = false

console.log(str1 == '')
console.log(str2 == '')
console.log(str3 == '')

Output:

true
true
true

Use the length Property to Check if the String Is Empty in JavaScript

Here is another way to check JavaScript empty string. If the length is zero, then we know that the string is empty.

Example:

let str1 = 'Hello world!';
let str2 = '';
let str3 = 4;
console.log(str1.length === 0)
console.log(str2.length === 0)
console.log(str3.length === 0)

Output:

false
true
false

Convert the Variable to Boolean to Check if the String Is Empty in JavaScript

There are two ways to convert variables to a Boolean value. First by dual NOT operators (!!), and Second by typecasting (Boolean(value)).

Boolean(str);

!!str;

The str is a variable. It returns false for null, undefined, 0, 000, "" and false. It returns true for not empty string and whitespace.

Example:

let str1 = 'Hello world!';
let str2 = '';
console.log(!!str1)
console.log(!!str2)
console.log(Boolean(str1))
console.log(Boolean(str2))

Output:

true
false
true
false