Easy methods to use the Fetch API in Node.js, Deno, and Bun — SitePoint







On this article, we’ll have a look at methods to use the Fetch API with Node.js, Deno, and Bun.

Desk of Contents

Fetch API vs XMLHttpRequest

Fetching information through an HTTP request is prime internet utility exercise. You will have made such calls within the browser, however the Fetch API is natively supported in Node.js, Deno, and Bun.

In a browser, you may request data from a server so you’ll be able to show it and not using a full display refresh. That is usually often known as an Ajax request or a single web page utility (SPA). Between 1999 and 2015, XMLHttpRequest was the one possibility — and stays so if you wish to present file add progress. XMLHttpRequest is a reasonably clunky callback-based API, however it permits fine-grained management and, regardless of the identify, it’ll deal with responses in codecs apart from XML — comparable to textual content, binary, JSON, and HTML.

Browsers have carried out the Fetch API from 2015. It’s a less complicated, simpler, extra constant, promise-based various to XMLHttpRequest.

Your server-side code might also wish to make HTTP requests — usually to name APIs on different servers. From their first launch, each the Deno and Bun runtimes usefully replicated the browser’s Fetch API in order that related code may run on each the shopper and server. Node.js required a third-party module comparable to node-fetch or axios till February 2022, when model 18 added the usual Fetch API. It’s nonetheless thought-about experimental, however now you can use fetch() all over the place with an identical code normally.

A Fundamental Fetch Instance

This straightforward instance fetches response information from a URI:

const response = await fetch('https://instance.com/information.json');

The fetch() name returns a promise which resolves with a Response object offering details about the consequence. You possibly can parse the HTTP response physique right into a JavaScript object utilizing the promise-based .json() methodology:

const information = await response.json();

Shopper-side vs Server-side Fetch

The API could also be an identical throughout platforms, however browsers implement restrictions when making client-side fetch() requests:

  • Cross-origin useful resource sharing (CORS)

    Shopper-side JavaScript can solely talk with API endpoints inside its personal area. A script loaded from https://domainA.com/js/primary.js can name any service at https://domainA.com/, comparable to https://domainA.com/api/ or https://domainA.com/information/.

    It’s unattainable to name a service on https://domainB.com/ — until that server permits entry by setting an HTTP Entry-Management-Permit-Origin header.

  • Content material Safety Coverage (CSP)

    Your web pages/apps can set a Content material-Safety-Coverage HTTP header or meta tag to regulate permitted belongings in a web page. It might probably forestall unintentional or malicious injection of scripts, iframes, fonts, photographs, movies, and so forth. For instance, setting default-src 'self' stops fetch() requesting information exterior its personal area (XMLHttpRequest, WebSocket, server-sent occasions, and beacons are additionally restricted).

Server-side Fetch API calls in Node.js, Deno, and Bun have fewer restrictions, and you may request information from any server. That mentioned, third-party APIs could:

  • require some type of authentication or authorization utilizing keys or OAuth
  • have most request thresholds, comparable to no a couple of name per minute, or
  • make a business cost for entry

You should utilize server-side fetch() calls to proxy client-side requests so you’ll be able to keep away from CORS and CSP points. That mentioned, bear in mind to be a conscientious internet citizen and don’t bombard providers with 1000’s of requests that might take them down!

Customized Fetch Requests

The instance above requests information from the URI https://instance.com/information.json. Under the floor, JavaScript creates a Request object, which represents the total particulars of that request comparable to the strategy, headers, physique, and extra.

fetch() accepts two arguments:

  • the useful resource – a string or URL object, and
  • an non-compulsory choices parameter with additional request settings

For instance:

const response = await fetch('https://instance.com/information.json', {
   methodology: 'GET',
   credentials: 'omit',
   redirect: 'error',
   precedence: 'excessive'

The choices object can set following properties in Node.js or client-side code:

property values
methodology GET (the default), POST, PUT, PATCH, DELETE, or HEAD
headers a string or Headers object
physique is usually a string, JSON, blob, and so forth.
mode same-origin, no-cors, or cors
credentials omit, same-origin, or embody cookies and HTTP authentication headers
redirect comply with, error, or handbook dealing with of redirects
referrer the referring URL
integrity subresource integrity hash
sign an AbortSignal object to cancel the request

Optionally, you’ll be able to create a Request object and move it to fetch(). This can be sensible in the event you can outline API endpoints upfront or wish to ship a collection related requests:

const request = new Request('https://instance.com/api/', {
  methodology: 'POST',
  physique: '{"a": 1, "b": 2, "c": 3}',
  credentials: 'omit'

console.log(`fetching ${ request.url }`);
const response = await fetch(request);

Dealing with HTTP Headers

You possibly can manipulate and look at HTTP headers within the request and response utilizing a Headers object. The API can be acquainted in the event you’ve used JavaScript Maps:

const headers = new Headers({
  'Content material-Sort': 'textual content/plain',

headers.append('Authorization', 'Fundamental abc123');

headers.set('Content material-Sort', 'utility/json');

const sort = headers.get('Content material-Sort');

if (headers.has('Authorization')) {



headers.forEach((worth, identify) => {
  console.log(`${ identify }: ${ worth }`);

const response = await fetch('https://instance.com/information.json', {
   methodology: 'GET',

response.headers.forEach((worth, identify) => {
  console.log(`${ identify }: ${ worth }`);

Fetch Promise Resolve and Reject

You may presume a fetch() promise will reject when an endpoint returns a 404 Not Discovered or related server error. It doesn’t! The promise will resolve, as a result of that decision was profitable — even when the consequence wasn’t what you anticipated.

A fetch() promise solely rejects when:

  • you make an invalid request — comparable to fetch('httttps://!invalidURL/');
  • you abort the fetch() request, or
  • there’s a community error, comparable to a connection failure

Analyzing Fetch Responses

Profitable fetch() calls return a Response object containing details about the state and returned information. The properties are:

property description
okay true if the response was profitable
standing the HTTP standing code, comparable to 200 for achievement
statusText the HTTP standing textual content, comparable to OK for a 200 code
url the URL
redirected true if the request was redirected
sort the response sort: primary, cors, error, opaque, or opaqueredirect
headers the response Headers object
physique a ReadableStream of physique content material (or null)
bodyUsed true if the physique has been learn

The next Response object strategies all return a promise, so you need to use await or .then blocks:

methodology description
textual content() returns the physique as a string
json() parses the physique to a JavaScript object
arrayBuffer() returns the physique as an ArrayBuffer
blob() returns the physique as a Blob
formData() returns the physique as a FormData object of key/worth pairs
clone() clones the response, usually so you’ll be able to parse the physique in several methods

const response = await fetch('https://instance.com/information.json');

if ( response.okay && response.headers.get('Content material-Sort') === 'utility/json') {

   const obj = await response.json();


Aborting Fetch Requests

Node.js gained’t trip a fetch() request; it may run perpetually! Browsers can even wait between one and 5 minutes. It’s best to abort fetch() beneath regular circumstances the place you’re anticipating a fairly fast response.

The next instance makes use of an AbortController object, which passes a sign property to the second fetch() parameter. A timeout runs the .abort() methodology if fetch doesn’t full inside 5 seconds:

  controller = new AbortController(),
  sign = controller.sign,
  timeout = setTimeout(() => controller.abort(), 5000);

strive {

  const response = await fetch('https://instance.com/slowrequest/', { sign });


  console.log( response.okay );

catch (err) {



Node.js, Deno, Bun, and most browsers launched since mid-2022 additionally assist AbortSignal. This presents a less complicated timeout() methodology so that you don’t should handle your individual timers:

strive {

  const response = await fetch('https://instance.com/slowrequest/', {
    sign: AbortSignal.timeout( 5000 ),

  console.log( response.okay );

catch (err) {



Efficient Fetches

Like all asynchronous, promise-based operation, you need to solely make fetch() calls in collection when the enter of a name relies on the output of a earlier one. The next code doesn’t carry out in addition to it may as a result of every API name should look ahead to the earlier one to resolve or reject. If every response takes one second, it’ll take a complete of three seconds to finish:

const response1 = await fetch('https://example1.com/api/');
const response2 = await fetch('https://example2.com/api/');
const response3 = await fetch('https://example3.com/api/');

The Promise.allSettled() methodology runs guarantees concurrently and fulfills when all have resolved or rejected. This code completes on the pace of the slowest response. Will probably be thrice quicker:

const information = await Promise.allSettled(
  ].map(url => fetch( url ))

information returns an array of objects the place:

  • every has a standing property string of "fullfilled" or "rejected"
  • if resolved, a worth property returns the fetch() response
  • if rejected, a motive property returns the error


Until you’re utilizing a legacy model of Node.js (17 or beneath), the Fetch API is out there in JavaScript on each the server and shopper. It’s versatile, straightforward to make use of, and constant throughout all runtimes. A 3rd-party module ought to solely be essential in the event you require extra superior performance comparable to caching, retries, or file dealing with.


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