React API Calls (Fetch & Axios)

API calls are used in React to retrieve or send data to a server. The most common ways to make HTTP requests are using the Fetch API (built-in) and Axios (third-party library).

Where to Make API Calls in React

API calls are usually made inside the useEffect hook to avoid repeated requests.

useEffect(() => {
  // API call here
}, []);

Using Fetch API

Basic GET Request

import { useEffect, useState } from "react";

function Users() {
  const [users, setUsers] = useState([]);

  useEffect(() => {
    fetch("https://api.example.com/users")
      .then(response => response.json())
      .then(data => setUsers(data))
      .catch(error => console.error(error));
  }, []);

  return (
    <ul>
      {users.map(user => (
        <li key={user.id}>{user.name}</li>
      ))}
    </ul>
  );
}

POST Request with Fetch

fetch("https://api.example.com/users", {
  method: "POST",
  headers: {
    "Content-Type": "application/json"
  },
  body: JSON.stringify({ name: "Alice" })
});

Using Axios

Installation

npm install axios

Basic GET Request

import axios from "axios";

useEffect(() => {
  axios.get("https://api.example.com/users")
    .then(res => setUsers(res.data))
    .catch(err => console.error(err));
}, []);

POST Request with Axios

axios.post("https://api.example.com/users", {
  name: "Alice"
});

Fetch vs Axios

Handling Loading and Errors

const [loading, setLoading] = useState(true);
const [error, setError] = useState(null);

useEffect(() => {
  fetch(url)
    .then(res => res.json())
    .then(data => {
      setData(data);
      setLoading(false);
    })
    .catch(err => {
      setError(err.message);
      setLoading(false);
    });
}, []);

Using Async/Await

useEffect(() => {
  async function fetchData() {
    try {
      const res = await axios.get(url);
      setData(res.data);
    } catch (err) {
      console.error(err);
    }
  }

  fetchData();
}, []);

Cleanup & Abort (Advanced)

useEffect(() => {
  const controller = new AbortController();

  fetch(url, { signal: controller.signal });

  return () => controller.abort();
}, []);

Best Practices

• Use useEffect for API calls

• Handle loading and error states

• Clean up requests on unmount

• Separate API logic when possible

Key Points

• API calls fetch data from servers

• Fetch and Axios are common tools

• Axios simplifies request handling

• Always handle loading & errors