March 30, 2022

How to Check if String is Not Empty or Whitespace in Javascript

By Krishnaa JavaScript Questions 0 Comments

In this tutorial, you will learn how to check if string is not empty or whitespace in javascript. A string is considered to be empty when it does not have any characters or content in it and as a result, the length of that string will always be 0. But when it comes to spaces, they are considered as valid content and the length of the string will never be zero.

There are numerous ways to check if a string is not empty or whitespace. But for the sake of simplicity, we will use a strict equality operator (===), logical NOT(!) operator, trim() method, and ternary (?) operator to accomplish our goal.

The ternary operator is also known as the conditional operator which acts similar to the if-else statement. The trim() method returns a new string after removing spaces at the beginning and the end of a given string.

In the following example, we have one global variable that holds a string. Upon click of a button, we will check if the string is not empty or whitespace and display the result on the screen. Please have a look over the code example and the steps given below.

HTML & CSS

We have 3 elements in the HTML file (div, button, and h1). The div element is just a wrapper for the rest of the elements.
The innerText for the button element is “Check” and for the h1 element, it is “Result”.
We have done some basic styling using CSS and added the link to our style.css stylesheet inside the head element.
We have also included our javascript file script.js with a script tag at the bottom.

<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <link rel="stylesheet" href="style.css">
  <title>Document</title>
</head>

<body>

  <div class="container">    
    <button>Check</button>
    <h1>Result</h1>
  </div>

  <script src="script.js"></script>
</body>

</html>

.container {        
    text-align: center;
}

button {
  margin-top: 10px;
  padding: 10px 20px;
}

Javascript

We have selected the button element and h1 element using the document.querySelector() method and stored them in btnCheck and output variables respectively.
We have attached a click event listener to the button element.
We have a global variable myString which holds an empty string as its value.
In the event handler function, we are using strict equality operator (===), trim() method and logical NOT (!) operator to check if myString is not empty or whitespace. Depending upon the result of the check, we will assign “Valid” or “Invalid” to the result variable.
We are displaying the result in the h1 element using the innerText property.

let btnCheck = document.querySelector("button");
let output = document.querySelector("h1");

let myString = "Hello World";

btnCheck.addEventListener("click", () => { 
  
  let result = myString.trim() !== "" ? "Valid" : "Invalid";
  output.innerText = result;
  
});

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