JS Bites: Chapter 4 - Fetch API

Fetch API

fetch()is a function used to send the requests to APIs and retrieve data.

const response = fetch('someapi.com');

How Does It Work?

When you pass the URL to fetch(), JavaScript creates a request object internally.

// Internal working
const request = new Request('someapi.com', {
   method: 'GET'   
});

const response = fetch(request);

The above demonstrates the initial workings of fetch(), abstracting away the complexities for you.

Response Object

fetch() is asynchronous, returning a promise that resolves later.

const url = "https://jsonplaceholder.typicode.com/todos/1"; 

async function fetchData() {
    const response = await fetch(url);
    console.log(response);
}

fetchData();

This will output the response object. To obtain data, you need to convert the response object into JSON.

const url = "https://jsonplaceholder.typicode.com/todos/1";

async function fetchData() {
    const response = await fetch(url); 
    const data = await response.json();
    console.log(data.title);
}

fetchData();

GET Requests Parameters

For specific data, parameters can be added to the URL, but this method isn’t secure, For safety, include parameters in the request object.

const url = 'someUrl';

async function getData() {
    const request = new Request(url, {
        headers: {
            'Authorization': 'token'    
        }
    });

    const response = await fetch(request);
    const data = await response.json();
    console.log(data);
}

getData();

Error Handling

Handle errors properly. If the request is successful but the data retrieval fails. it’s still considered a success.

let’s handle the error if the request is made successfully but the data retrieval fails. Check the status code for error handling.

try {
    const response = await fetch(request);
    if (response.status === 200) {
        const data = await response.json(); 
        console.log('Success', data);
    } else {
        console.log('Server error', data.error.message);
    }
} catch(error) {
    console.log(error);
}

POST Request

When you send data to a server, like when submitting a form, you can use the POST method. To do this with fetch(), you need to include the data you want to send in the request body.

const request = new Request(url, {
    headers: {...},
    body: {...}
});

For more detailed information on the Fetch API, refer to the MDN documentation.

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JS Bites: Chapter 4 - Fetch API

Sanjay R

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