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How to truncate numbers in ReactJS

Getting Started with Truncating Numbers in ReactJS

ReactJS is a popular JavaScript library for building user interfaces, and it's highly utilized for single-page applications. One common need in these applications is to truncate numbers for a better display. Truncation simply refers to shortening a number by dropping the extra digits after a certain point.

In this blog post, we'll explore how to truncate numbers in ReactJS effectively. We will break it down step by step, providing code examples along the way. You don't need to be an expert to follow along, but a basic understanding of JavaScript and ReactJS will be helpful.

What is Number Truncation?

Before we dive into the code, let's understand what number truncation is. Imagine you have a long piece of rope and you want to shorten it. You would cut off a part of it, right? That's exactly what we do in number truncation. We "cut off" the digits we don't need.

For example, if we have the number 123.456 and we want to truncate it to two decimal places, the result would be 123.45. The .006 is cut off, or truncated.

Why Truncate Numbers?

Number truncation is often used in scenarios where displaying a full number would be unnecessary or confusing. For example, in a weather app, displaying the temperature as 20.12345678 degrees isn't practical. It's more user-friendly to truncate the temperature to 20.12 degrees.

Truncating Numbers in ReactJS

Now that we understand what number truncation is and why it's useful, let's dive into how we can achieve this in ReactJS.

Step 1: Create a New React App

First, we need to create a new React app. We will use the create-react-app command for this. Open your terminal and run:

npx create-react-app truncating-numbers

This will create a new React app called "truncating-numbers".

Step 2: Create a Function to Truncate Numbers

Next, let's create a function to truncate numbers. In your App.js file, add the following function:

function truncateNumber(number, decimalPlaces) {
    const factor = Math.pow(10, decimalPlaces);
    return Math.floor(number * factor) / factor;

This function takes two parameters: the number to truncate and the number of decimal places to keep. The Math.pow(10, decimalPlaces) part is like moving the decimal point decimalPlaces places to the right. Then, Math.floor(number * factor) chops off the extra digits, and finally we move the decimal point back by dividing by factor.

Step 3: Use the Truncate Function in a Component

Now we can use our truncateNumber function in a React component. Let's create a simple component that displays a truncated number:

function TruncatedNumber({ number, decimalPlaces }) {
    const truncated = truncateNumber(number, decimalPlaces);

    return <p>The truncated number is {truncated}</p>;

This TruncatedNumber component takes two props: the number to truncate and the number of decimal places to keep. It calls our truncateNumber function and then displays the result.

Step 4: Use the TruncatedNumber Component in App

Finally, let's use our TruncatedNumber component in the App component:

function App() {
    return (
        <div className="App">
            <TruncatedNumber number={123.456} decimalPlaces={2} />

Now our app will display "The truncated number is 123.45".


Truncating numbers in ReactJS doesn't have to be complicated. With just a simple function and a few lines of code, we can easily truncate numbers to a specified number of decimal places.

As you continue to learn and grow as a programmer, remember that these simple tasks are the building blocks of larger, more complex applications. Don't be afraid to dive in, experiment, and learn from your mistakes. It's like playing with building blocks. You start with simple structures, but before you know it, you're building entire cities.

So, keep learning, keep building, and keep truncating those numbers. Who knows? You might find yourself cutting down those long numbers like a pro, making your apps more user-friendly and efficient. And perhaps, in this journey of number truncation, you might find your path to becoming a ReactJS master! Happy coding!