September 13, 2022

How to Change Positive Number to Negative in Javascript

By Krishnaa JavaScript Questions 0 Comments

In this tutorial, you will learn how to change positive number to negative in javascript. Making calculations without using numbers is challenging. You can create a number by combing the digits 0 through 9. For a newbie developer, it can be a bit tricky to change positive number to negative number.

There are numerous ways to change positive number to negative number. But for the sake of simplicity, we will make use of Math object. This object contains a lot of methods and properties which can help us in various mathematical operations. One of those methods is the abs() method.

The abs() method returns an absolute value of a number. Finding a number’s distance from zero will allow you to establish its absolute value regardless of which way it is moving along the number line. A number’s absolute value is its value after any prior negative sign has been eliminated. The absolute value of -7 is 7.

In the following example, we have an input field in which we will enter a random number. Upon click of a button, we will change positive number to negative number and display that on the screen. Please have a look over the code example and the steps given below.

HTML & CSS

We have 4 elements in the HTML file (div, input, button, and h1). The div element is just a wrapper for the rest of the elements.

The innerText for the button element is “Get” 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">
    <input type="number" placeholder="Enter Number">
    <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;
}

input {
  display: block;  
  margin: 10px auto;
  padding: 10px 20px;
}

input[type=number]::-webkit-inner-spin-button, 
input[type=number]::-webkit-outer-spin-button { 
  -webkit-appearance: none; 
  margin: 0; 
}

Javascript

We have selected the input element, button element, and h1 element using the document.querySelector() method and stored them in input, btnGet, and output variables respectively.
We have attached a click event listener to the button element.

In the event handler function, we are storing the value of the input element in the num variable.
We are calling the abs() method to get the absolute of num and we are prefixing it with negative sign. We are storing the number in the result variable.
We are displaying the result in the h1 element using the innerText property.

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

btnGet.addEventListener("click", () => {
  let num = input.value;
  let result = -Math.abs(num);
  output.innerText = result;
});

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