2 ways to loop through a number in React

In this article, we will discuss 2 ways how you can loop through a number in React.

While developing frontend of an application 🖥, you might encounter a situation where you have to display a list of data. For example, a list of users etc.

Most common way to loop through an array in React is using Javascript built-in map function.

But if you have a number that you have to loop through. For example, run a loop till 10 etc.

In this case, we have 2 options.

1st way: Using function ☑️

One way to loop through a number in React is to create a function that will:

• Create an array.
• Using basic for loop and push the HTML code in array.
• Return the array.

Here is the code on how to do that. 👨🏻‍💻

function App() {

    const [number, setNumber] = React.useState(10);

    function renderLoop() {
        const elements = [];

        for (let a = 0; a < number; a++) {
            elements.push(
                <p key={ `1st-way-${ a }` }>{ a }</p>
            );
        }

        return elements;
    }

    return (
        <>
            { renderLoop() }
        </>
    );
}

Following will be the output of above code:

0
1
2
3
4
5
6
7
8
9

2nd way: Using map ✅

Javascript’s map function can also be used to iterate over an array and display a list without having to create a function.

function App() {

    const [number, setNumber] = React.useState(10);

    return (
        <>
            { Array.from({ length: number }, function (_, index) { return index })
                .map(function (n) {
                    return (
                        <p key={ `2nd-way-${ n }` }>{ n }</p>
                    )
            }) }
        </>
    );
}

Explanation 🕵🏻‍♂️

• The first argument of Array.from is an object that will create an array of length 10 such that each element has an index starting from 0.
• The second argument is a mapping function.
  • First parameter is “_” which means the value.
  • Second parameter is “index”.
  • It is returning the index without any modification, so the original number will be returned.
  • It will create an array from 0 to 9.
• Using the map function, you can perform some action on that array created from number. In this case, we are displaying each number n in a paragraph. 📄

So that’s how you can loop through a number in React. If you face any problem in following this, kindly do let me know. 💬