July 13, 2022

How to Add Prefix to a String in Javascript

By Krishnaa JavaScript Questions 0 Comments

In this tutorial, you will learn how to add prefix to a string in javascript. A string is made up of many characters. Prefixes are a particular kind of affix that appear at the start of a word and change its meaning. For a newbie developer, it can be a bit tricky to add prefix to a string.

There are numerous ways to add prefix to a string. But for the sake of simplicity, we will make use of addition operator (+) which helps in concatenating two individual strings.

In the following example, we have one global variable that holds a string. Upon click of a button, we will add prefix to a string 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 “Add” 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>Add</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 btnAdd and output variables respectively.
We have a global variable myString which holds a string as its value.
We are displaying myString in the h1 element using innerText property.
We have attached a click event listener to the button element.
In the event handler function, we have prefix"Keep" stored in the myPrefix variable. We are adding it to the myString using addition operator (+) and storing the final string in the result variable.
We are displaying the result in the h1 element using the innerText property.

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

let myString = ` it up`;
output.innerText =  myString;
 
btnAdd.addEventListener("click", () => {  
  let myPrefix = "Keep"
  let result = myPrefix + myString;
  output.innerText = result;
});

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