April 9, 2022

How to Check if a String Contains Certain Characters in Javascript

By Krishnaa JavaScript Questions 0 Comments

In this tutorial, you will learn how to check if a string contains certain characters in javascript. A string consists of multiple characters and these characters can be letters, numbers, or special characters. For a beginner, it can be a bit tricky to find if it contains certain characters.

There are numerous ways to check if a string contains certain characters. But for the sake of simplicity, we will use split() method, toLowerCase() method, include() method, every() method and ternary operator (?) to accomplish our goal.

The split() method splits a given string into multiple substrings and returns an array of those substrings. The toLowerCase() method converts all letters in a string to lowercase. 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 every() method executes a certain function for each element in an array. The every() method returns true if the returned value of the function is true for all elements.

In the following example, we have one global variable that holds a string. Upon click of a button, we will check if the string contains certain characters 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 2 global variables myString and characters. We need to check if myString contains all the characters present in the characters variable.
In the event handler function, we are calling the split() method and storing the returned array in the charArray variable.
We are calling every() method on charArray and looping through each element in the array. We are using includes() to check if the character is present in the myString.
We are performing here case-insensitive check by calling the toLowerCase() method on the character as well as on the myString. You can remove this method if you want to perform a case-sensitive check.
After the completion, every() method will return either true or false. We are storing that in the hasCharacters variable. If it is true, that means myString does contain specific characters.
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 = "A quick brown fox jumps over the lazy dog";
let characters = "ojdg";

btnCheck.addEventListener("click", () => {
  let charArray = characters.split("");
  let hasCharacters = charArray.every((c) =>
    myString.toLowerCase().includes(c.toLowerCase())
  );
  let result = hasCharacters ? "Yes" : "No";
  output.innerText = result;
});

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