April 15, 2022

How to Check if String Not Contains Substring in Javascript

By Krishnaa JavaScript Questions 0 Comments

In this tutorial, you will learn how to check if string not contains substring in javascript. A subset of a string is known as a substring. For example, “test” is a substring of “This is test string”.

There are numerous ways to check if a string not contains substring. But for the sake of simplicity, we will use the includes() method, NOT logical operator (!) and ternary operator (?) to accomplish our goal.

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 NOT logical operator (!) reverses the result of any given expression or condition. The ternary operator is also known as the conditional operator which acts similar to the if-else statement.

In the following example, we have one global variable that holds a string. Upon click of a button, we will check if the string not contains substring 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 are using the includes() method, NOT logical operator (!), and ternary operator (?) to check if myString not contains “test” substring.
Depending upon the result of the check, we will assign “Not Contains” or “Contains” 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.includes("test") ? "Not Contains" : "Contains";
  output.innerText = result;
  
});

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