How do you loop inside React JSX?

Naveera A.

—October 21, 2022

The ProblemThe Problem

You have a set of elements, and you’d like to loop over them to generate a JSX partial.

In templating languages, you can write a for loop directly inside the template. For example, you can use the following code to loop over a list in Jinja:

{% for i in range(11) %}
    <li>{{ i }}</li>
{% endfor %}

How can you do the same thing using JSX?

The SolutionThe Solution

Two ways you can loop inside JSX are using traditional loops or using the map() method.

Using Traditional LoopsUsing Traditional Loops

If you have a set of elements, you can use normal JavaScript for, for of, and for in loops outside the return block.

Inside the return block, you can use the resulting array.

You can loop over an array and create JSX partials like so:

import React from "react";

function App() {
  const seasons = ["Spring", "Summer", "Autumn", "Winter"];

  let seasonsList = [];

  seasons.forEach((season, index) => {
    seasonsList.push(<li key={index}>{season}</li>);
  });

  return (
    <div>
      <h2>Seasons of the year</h2>
      <ul>{seasonsList}</ul>
    </div>
  );
}

export default App;

Using the map() MethodUsing the map() Method

You can use the map() method on an array to loop through the elements and create components, or generate JSX, inside the return block.

import React from "react";

function App() {
  const seasons = ["Spring", "Summer", "Autumn", "Winter"];

  return (
    <div>
      <h2>Seasons of the year</h2>
      <ul>
        {seasons.map((season) => (
          <li key={season.id}>{season}</li>
        ))}
      </ul>
    </div>
  );
}

export default App;

Many developers prefer using map() to loop over arrays.

Further ReadingFurther Reading

If you’re looking to get a deeper understanding of how React application monitoring works, take a look at the following articles:

• React Debugging Hub
• How to Install the Sentry React SDK in 60 SecondsYoutube
• React Native with Robin Heinze
• Sentry for React
• React Error and Performance Monitoring
• Why the jQuery Creator Uses React and Typescript - John Resig