September 25, 2022

How to Round Decimal Numbers in Javascript

By Krishnaa JavaScript Questions 0 Comments

In this tutorial, you will learn how to round decimal numbers in javascript. Despite the fact that decimal values provide a number’s exact value, there are times when a whole number, rather than a decimal number, is all that is required. From a developer perspective, it can be a bit tricky to round decimal numbers.

There are numerous ways to round decimal numbers. We are going to use the simplest approach which involves the usage of the Math object. This object contains round() method which returns a nearest integer after rounding the number.

In the following example, we have one global variable that holds a decimal number. Upon click of a button, we will round the decimal numbers 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 “Round”.
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>Round</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 btnRound and output variables respectively.
We have attached a click event listener to the button element.
We have a global variable myNum which holds a decimal number as its value.
We are displaying the original number in the h1 element using the innerText property.
In the event handler function, we are calling round() method of Math object and passing myNum as a parameter. As a result, it will round the number to the nearest integer and returns that.
The returned value is stored in the result variable.
We are displaying the result in the h1 element using the innerText property.

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

let myNum= 3223.25;

output.innerText = myNum;

btnRound.addEventListener("click", () => {
  let result = Math.round(myNum);
  output.innerText = result;
});

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