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How to get the first non-null/undefined argument in JavaScript ?

How to Check empty/undefined/null String in JavaScript?

Last Updated : 17 Nov, 2024

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Empty strings contain no characters, while null strings have no value assigned. Checking for an empty, undefined, or null string in JavaScript involves verifying if the string is falsy or has a length of zero. Here are different approaches to check a string is empty or not.

1. Using === Operator

Using === operator we will check the string is empty or not. If empty then it will return “Empty String” and if the string is not empty it will return “Not Empty String”.

Syntax

if (str === "") {    
    console.log("Empty String")
} else {
    console.log("Not Empty String")
}

JavaScript

// Function to check string is empty or not function checking(str){  	// Checking the string using === operator     if (str === "") {         console.log("Empty String")     }     else {        console.log("Not Empty String")     } }  // Checking for empty string checking(""); checking("GeeksforGeeks");

Output

Empty String Not Empty String

2. Using length and ! Operator

This approach uses length property to get the length of string and ! operator. and by using ! operator we will check string is empty or not.

JavaScript

// Function to check string is empty or not function checking(str) {     return (!str || str.length === 0 ); }  console.log(checking("")); console.log(checking("GeeksforGeeks"));

Output

true false

3. Using replace() Method

This approach uses replace() Method. It will ensure that the string is not just a group of empty spaces where we are doing replacement on the spaces.

JavaScript

// function to check string is empty or not function checking(str) {     if(str.replace(/\s/g,"") == "") {         console.log("Empty String")     }     else{         console.log("Not Empty String")     } }  checking("  "); checking("Hello Javascript");

Output

Empty String Not Empty String

How to get the first non-null/undefined argument in JavaScript ?

A

AmanAgarwal6

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Article Tags :

JavaScript
Web Technologies

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