How to Change Lowercase to Uppercase in Javascript

In this tutorial, you will learn how to change lowercase to uppercase in javascript. Sometimes it is very important to change the lowercase string to an uppercase string before sending it for further processing. From a developer perspective, it can be a bit tricky to change lowercase string to an uppercase string.

There are numerous ways to change lowercase string to an uppercase string. We are going to use the simplest approach which involves the usage of  toUpperCase() method. This method will simply convert the string to an uppercase string and return a new string.

In the following example, we have one global variable that holds a string. Upon click of a button, we will change the lowercase string to an uppercase 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 “Get”.
  • 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>Get</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 btnGet 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.
  • We are displaying the original string in the h1 element using the innerText property.
  • In the event handler function, we are calling toUpperCase() method. As a result, it will change the lowercase string to an uppercase string. The new string returned by this method will be stored in the result variable.
  • We are displaying the result in the h1 element using the innerText property.
let btnGet = document.querySelector("button");
let output = document.querySelector("h1");

let myString = "i think you are not serious";

output.innerText = myString;

btnGet.addEventListener("click", () => {
  let result = myString.toUpperCase();
  output.innerText = result;
});