How to write loops in React

By Tom Hastjarjanto

Introduction

In this post I will show you how to write loops in React. I will show you how to write loops in React using the map function and I will show you how to write loops in React using the for loop.

Write loops in React using map

The map function is used to loop over an array in React. In this example I will show you how to write loops in React using the map function.

import React from "react";

export default function LoopsInReact() {
  const data = [
    { id: 1, title: "Buy milk", completed: false },
    { id: 2, title: "Buy bread", completed: true },
    { id: 3, title: "Buy eggs", completed: false },
  ];

  return (
    <div className="App">
      <ul>
        {data.map((item) => (
          <li key={item.id}>
            {item.title} {item.completed ? "✅" : "❌"}
          </li>
        ))}
      </ul>
    </div>
  );
}

Write loops in React using for loop

The for loop is used to loop over an array in React. In this example I will show you how to write loops in React using the for loop.

import React from "react";

export default function LoopsInReact() {
  const data = [
    { id: 1, title: "Buy milk", completed: false },
    { id: 2, title: "Buy bread", completed: true },
    { id: 3, title: "Buy eggs", completed: false },
  ];

  return (
    <div className="App">
      <ul>
        {(() => {
          const items = [];
          for (let i = 0; i < data.length; i++) {
            const item = data[i];
            items.push(
              <li key={item.id}>
                {item.title} {item.completed ? "✅" : "❌"}
              </li>
            );
          }
          return items;
        })()}
      </ul>
    </div>
  );
}

The key attribute

The key attribute is used to identify each element in a list. React uses the key attribute to identify which items have changed, are added, or are removed. The key attribute is required when using the map function.

Conclusion

In this post I showed you how to write loops in React. I showed you how to write loops in React using the map function and I showed you how to write loops in React using the for loop.

Further reading