April 19, 2022

How to Check if String Contains Substring (Case Insensitive) in Javascript

By Krishnaa JavaScript Questions 0 Comments

In this tutorial, you will learn how to check if string contains substring (case insensitive) in javascript. A subset of a string is known as a substring. For example, “test” is a substring of “My test”. From a developer perspective, it can be a bit tricky to find if a string contains a substring (case insensitive).

There are numerous ways to check if a string contains a substring (case insensitive). But for the sake of simplicity, we will use includes() method, toLowerCase() method, and ternary operator (?).

The includes() method is used to perform a case-sensitive search to detect whether a string contains another string or not and returns a Boolean value. The toLowerCase() method converts all letters in a string to lowercase.

In the following example, we have one global variable that holds a string. Upon click of a button, we will check if it contains a substring (case insensitive) 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 a string as its value.
In the event handler function, we have str variable that hold a substring as its value. We will check if myString contains str.
We are converting both the strings into lowercase by calling toLowerCase() method so that we can perform case-insensitive check.
Further, we are using the includes() method to verify whether myString contains str substring or not. If it returns true, that means myString does contain str substring.
Depending upon the result of the check, we will assign “Yes” or “No” 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 str = "orld",
  let result = myString.toLowerCase().includes(str.toLowerCase()) ? "Yes" : "No";
  output.innerText = result;
  
});

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