You may not need Axios

Fetch API to the rescue!

You may not need Axios

This is not an attack on Axios.
Rather, it’s advocacy for the fetch API which has become quite capable. 🦄

Overview

This article is a collection of the “missing” fetch code snippets and common use cases I wish were easier to find.

Overview
Feature Comparison
Fetch Recipes
Compatibility

Is your Use Case not listed? Let me know ✉️

Feature Comparison

	fetch	axios	request
Intercept request and response	✅	✅	✅
Transform request and response data	✅	✅	✅
Cancel requests	✅	✅	❌
Automatic transforms for JSON data	✅	✅	✅
Client side support for protecting against XSRF	✅	✅	✅
Progress	✅	✅	✅
Streaming	✅	✅	✅
Redirects	✅	✅	✅

When starting this article (late 2018, updated 2024) I assumed I’d end with a table of mixed check boxes. Surely there are special Use Cases which justified axios, request, r2, superagent, got, etc.

Well, as it turns out, I overestimated the need for 3rd party http libraries.

Despite using fetch for several years (including for non-trivial tasks: file uploads & error/retry support) I still had misconceptions of fetch’s abilities and limits.

Well, let’s check out what fetch can do…

Fetch Recipes

Get JSON from a URL

fetch('https://api.github.com/orgs/nodejs')
  .then(response => response.json())
  .then(data => {
    console.log(data) // result from `response.json()` above
  })
  .catch(error => console.error(error))

Custom headers

fetch('https://api.github.com/orgs/nodejs', {
  headers: new Headers({
    'User-agent': 'Mozilla/4.0 Custom User Agent'
  })
})
.then(response => response.json())
.then(data => {
  console.log(data)
})
.catch(error => console.error(error))

HTTP Error Handling

const isOk = response => response.ok ? response.json() : Promise.reject(new Error('Failed to load data from server'))


fetch('https://api.github.com/orgs/nodejs')
  .then(isOk) // <= Use `isOk` function here
  .then(data => {
    console.log(data) // Prints result from `response.json()`
  })
  .catch(error => console.error(error))

CORS example

CORS is primarily checked at the server - so make sure your configuration is correct on the server-side.

The credentials option controls if your cookies are automatically included.

fetch('https://api.github.com/orgs/nodejs', {
  credentials: 'include', // Useful for including session ID (and, IIRC, authorization headers)
})
.then(response => response.json())
.then(data => {
  console.log(data) // Prints result from `response.json()`
})
.catch(error => console.error(error))

Posting JSON

postRequest('http://example.com/api/v1/users', {user: 'Dan'})
  .then(data => console.log(data)) // Result from the `response.json()` call


function postRequest(url, data) {
  return fetch(url, {
    credentials: 'same-origin', // 'include', default: 'omit'
    method: 'POST',             // 'GET', 'PUT', 'DELETE', etc.
    body: JSON.stringify(data), // Use correct payload (matching 'Content-Type')
    headers: { 'Content-Type': 'application/json' },
  })
  .then(response => response.json())
  .catch(error => console.error(error))
}

Posting an HTML `<form>`

postForm('http://example.com/api/v1/users', 'form#userEdit')
  .then(data => console.log(data))


function postForm(url, formSelector) {
  const formData = new FormData(document.querySelector(formSelector))


  return fetch(url, {
    method: 'POST', // 'GET', 'PUT', 'DELETE', etc.
    body: formData  // a FormData will automatically set the 'Content-Type'
  })
  .then(response => response.json())
  .catch(error => console.error(error))
}

Form encoded data

To post data with a Content-Type of application/x-www-form-urlencoded we will use URLSearchParams to encode the data like a query string.

For example, new URLSearchParams({a: 1, b: 2}) yields a=1&b=2.

postFormData('http://example.com/api/v1/users', {user: 'Mary'})
  .then(data => console.log(data))


function postFormData(url, data) {
  return fetch(url, {
    method: 'POST', // 'GET', 'PUT', 'DELETE', etc.
    body: new URLSearchParams(data),
    headers: new Headers({
      'Content-type': 'application/x-www-form-urlencoded; charset=UTF-8'
    })
  })
  .then(response => response.json())
  .catch(error => console.error(error))
}

Uploading a file

postFile('http://example.com/api/v1/users', 'input[type="file"].avatar')
  .then(data => console.log(data))


function postFile(url, fileSelector) {
  const formData = new FormData()
  const fileField = document.querySelector(fileSelector)


  formData.append('username', 'abc123')
  formData.append('avatar', fileField.files[0])


  return fetch(url, {
    method: 'POST', // 'GET', 'PUT', 'DELETE', etc.
    body: formData  // Coordinate the body type with 'Content-Type'
  })
  .then(response => response.json())
  .catch(error => console.error(error))
}

Uploading multiple files

Setup a file upload element with the multiple attribute:

<input type='file' multiple class='files' name='files' />

Then use with something like:

postFile('http://example.com/api/v1/users', 'input[type="file"].files')
  .then(data => console.log(data))


function postFile(url, fileSelector) {
  const formData = new FormData()
  const fileFields = document.querySelectorAll(fileSelector)


  // Add all files to formData
  Array.prototype.forEach.call(fileFields.files, f => formData.append('files', f))
  // Alternatively for PHPeeps, use `files[]` for the name to support arrays
  // Array.prototype.forEach.call(fileFields.files, f => formData.append('files[]', f))


  return fetch(url, {
    method: 'POST', // 'GET', 'PUT', 'DELETE', etc.
    body: formData  // Coordinate the body type with 'Content-Type'
  })
  .then(response => response.json())
  .catch(error => console.error(error))
}

Timeouts

Here’s a generic Promise timeout, using the “Partial Application” pattern. It’ll work with any Promise interface. Don’t do too much work in the supplied promise chain, it will keep running - and any failures have a way of creating long term memory leaks.

function promiseTimeout(msec) {
  return promise => {
    const timeout = new Promise((yea, nah) => setTimeout(() => nah(new Error('Timeout expired')), msec))
    return Promise.race([promise, timeout])
  }
}


promiseTimeout(5000)(fetch('https://api.github.com/orgs/nodejs'))
  .then(response => response.json())
  .then(data => {
    console.log(data) // Prints result from `response.json()` in getRequest
  })
  .catch(error => console.error(error)) // Catches any timeout (or other failure)



////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////


// Alternative example:
fetchTimeout(5000, 'https://api.github.com/orgs/nodejs')
  .then(console.log)
// Alternative implementation:
function fetchTimeout(msec, ...args) {
  return raceTimeout(fetch(...args))


  function raceTimeout(promise) {
    const timeout = new Promise((yea, nah) => setTimeout(() => nah(new Error('Timeout expired')), msec))
    return Promise.race([promise, timeout])
  }
}

And a more complex example, featuring a tracking flag __timeout so you can intercept any costly work.

function promiseTimeout(msec) {
  return (promise) => {
    let isDone = false
    promise.then(() => isDone = true)
    const timeout = new Promise((yea, nah) => setTimeout(() => {
      if (!isDone) {
        promise.__timeout = true
        nah(new Error('Timeout expired'))
      }
    }, msec))
    return Promise.race([promise, timeout])
  }
}


promiseTimeout(5000)(fetch('https://api.github.com/orgs/nodejs'))
.then(response => response.json())
.then(data => {
  console.log(data) // Prints result from `response.json()` in getRequest
})
.catch(error => console.error(error))

Download Progress Helper

Upload Progress is currently a bit buggy outside of Chrome.

The Progress Handler technique shown below avoids wrapping the fetch call in a closure. 👍

progressHelper has the following interface (source available below)

const progressHelper = require('./progressHelper.js')


const handler = ({loaded, total}) => {
  console.log(`Downloaded ${loaded} of ${total}`)
}
// handler args: ({ loaded = Kb, total = 0-100% })
const streamProcessor = progressHelper(handler)
// => streamProcessor is a function for use with the response _stream_

Let’s look at a usage example:

// The progressHelper could be inline w/ .then() below...
const streamProcessor = progressHelper(console.log)


fetch('https://fetch-progress.anthum.com/20kbps/images/sunrise-progressive.jpg')
  .then(streamProcessor) // note: NO parentheses because `.then` needs to get a function
  .then(response => response.blob())
  .then(blobData => {
    // ... set as base64 on an <img src="base64...">
  })

A reusable image downloader might look like getBlob():

const getBlob = url => fetch(url)
  .then(progressHelper(console.log)) // progressHelper used inside the .then()
  .then(response => response.blob())

By the way, a Blob is a Binary Large Object.

It’s important to choose ONE of the 2 usage patterns below (they are functionally equivalent):

// OPTION #1: no temp streamProcessor var
fetch(...)
  .then(progressHelper(console.log))


// ⚠️ OR️ ️⚠️


// OPTION #2: define a `streamProcessor` to hold our console logger
const streamProcessor = progressHelper(console.log)
fetch(...)
  .then(streamProcessor)

My preference is Option #1. However, your scope design may force you to use Option #2.

Finally, here’s the last part of this recipe, our progressHelper:

Source: Progress Helper

function progressHelper(onProgress) {
  return (response) => {
    if (!response.body) return response


    let loaded = 0
    const contentLength = response.headers.get('content-length')
    const total = !contentLength ? -1 : parseInt(contentLength, 10)


    return new Response(
      new ReadableStream({
        start(controller) {
          const reader = response.body.getReader()
          return read()


          function read() {
            return reader.read()
              .then(({ done, value }) => {
                if (done) return void controller.close()
                loaded += value.byteLength
                onProgress({ loaded, total })
                controller.enqueue(value)
                return read()
              })
              .catch(error => {
                console.error(error)
                controller.error(error)
              })
          }
        }
      })
    )
  }
}

credit: Special thanks to Anthum Chris and his fantastic Progress+Fetch PoC shown here

Recursive Retry Helper

/**
 * A **Smarter** retry wrapper with currying!
 */
function retryCurry(fn, retriesLeft = 5) {
  const retryFn = (...args) => fn(...args)
    .catch(err => retriesLeft > 0
      ? retryFn(fn, retriesLeft - 1)
      : Promise.reject(err)
    })
  return retryFn
}


const getJson = (url) => fetch(url)
  .then(response => response.json())


// Usage
const retryGetJson = retryCurry(getJson, 3);


// Now you can pass any arguments through to your function!
retryGetJson('https://api.github.com/orgs/elite-libs')
  .then(console.log)
  .catch(console.error)

/** Basic retry wrapper for Promises */
function retryPromise(fn, retriesLeft = 5) {
  return fn()
    .catch(err => retriesLeft > 0
      ? retryPromise(fn, retriesLeft - 1)
      : Promise.reject(err)
    })
}


const getJson = (url) => fetch(url)
  .then(response => response.json())


// Usage
retry(() => getJson('https://api.github.com/orgs/elite-libs'))
  .then(console.log)
  .catch(console.error)

Handling HTTP Redirects

const checkForRedirect = (response) => {
  // Check for temporary redirect (307), or permanent (308)
  if (response.status === 307 || response.status === 308) {
    const location = response.headers.get('location')
    if (!location) {
      return Promise.reject(new Error('Invalid HTTP Redirect! No Location header.'));
    }
    // You can change the behavior here to any custom logic:
    //   e.g. open a "confirm" modal, log the redirect url, etc.
    return fetch(location)
      // Bonus: this will handle recursive redirects ✨
      .then(checkForRedirect)
  }
  return response
};


fetch('https://api.github.com/orgs/elite-libs')
  // Next line will handle redirects
  .then(checkForRedirect)
  .then(response => response.json())
  .then(console.log)
  .catch(console.error)

Canceling a fetch request

const httpWithTimeout = (timeout = 5000, url) => {
  const controller = new AbortController();
  // Set an Nsec cancellation timeout
  const timer = setTimeout(() => controller.abort(), timeout);


  return fetch(url, { signal: controller.signal })
    .then(response => {
      clearTimeout(timer); // not required but closes open ref
      return response.text();
    }).then(text => {
      console.log(text);
    });
}

Compatibility

As of 2022, the fetch API is widely supported in all modern browsers and in more recent versions of NodeJS v18+.

If you must support IE you can polyfill fetch with the github/fetch package (maintained by an awesome team at GitHub). It’s possible to go as far back as IE8 - Your mileage may vary.

Earlier NodeJS can take advantage of the the fetch API with the node-fetch package:

npm install node-fetch

After polyfill+node-fetch: 99.99% compatible ✅

Please Tweet at me if you have other Use Cases you’d like to see. ❤️

DanLevy.net

You may not need Axios

Fetch API to the rescue!

You may not need Axios

Overview

Feature Comparison

Fetch Recipes

Get JSON from a URL

Custom headers

HTTP Error Handling

CORS example

Posting JSON

Posting an HTML `<form>`

Form encoded data

Uploading a file

Uploading multiple files

Timeouts

Download Progress Helper

Source: Progress Helper

Recursive Retry Helper

Handling HTTP Redirects

Canceling a fetch request

Compatibility

Read More Shit, by Dan Levy ✨

Quiz: Destructuring Delights

Quiz: Regular Expressions Mastery

Quiz: Prove your SQL Skills!

How to lose a billion dollars super fast

You may not need Axios

Fetch API to the rescue!

You may not need Axios

Overview

Feature Comparison

Fetch Recipes

Get JSON from a URL

Custom headers

HTTP Error Handling

CORS example

Posting JSON

Posting an HTML <form>

Form encoded data

Uploading a file

Uploading multiple files

Timeouts

Download Progress Helper

Source: Progress Helper

Recursive Retry Helper

Handling HTTP Redirects

Canceling a fetch request

Compatibility

Read More Shit, by Dan Levy ✨

Quiz: Destructuring Delights

Quiz: Regular Expressions Mastery

Quiz: Prove your SQL Skills!

How to lose a billion dollars super fast

Posting an HTML `<form>`