Axios vs Fetch

Is Axios better than fetch()?

Without question, some developers prefer Axios over built-in APIs for their ease of use. But many overestimate the need for such a library. The fetch() API is perfectly capable of reproducing the key features of Axios, and it has the added advantage of being readily available in all modern browsers.

In this article, we will compare fetch() and Axios to see how they can be used to perform different tasks. Hopefully, by the end of the article, you’ll have a better understanding of both APIs.

Basic syntax

Before we delve into more advanced features of Axios, let’s compare its basic syntax to fetch().

Here’s how you can use Axios to send a POST request with custom headers to a URL. Axios automatically converts the data to JSON, so you don’t have to:

// axios

const url = 'https://jsonplaceholder.typicode.com/posts'
const data = {
  a: 10,
  b: 20,
};
axios
  .post(url, data, {
    headers: {
      Accept: "application/json",
      "Content-Type": "application/json;charset=UTF-8",
    },
  })
  .then(({data}) => {
    console.log(data);
});

Now compare this code to the fetch() version, which produces the same result:

// fetch()

const url = "https://jsonplaceholder.typicode.com/todos";
const options = {
  method: "POST",
  headers: {
    Accept: "application/json",
    "Content-Type": "application/json;charset=UTF-8",
  },
  body: JSON.stringify({
    a: 10,
    b: 20,
  }),
};
fetch(url, options)
  .then((response) => response.json())
  .then((data) => {
    console.log(data);
  });

Notice that:

• To send data, fetch() uses the body property for a post request to send data to the endpoint, while Axios uses the data property

• The data in fetch() is transformed to a string using the JSON.stringify method

• Axios automatically transforms the data returned from the server, but with fetch() you have to call the response.json method to parse the data to a JavaScript object

• With Axios, the data response provided by the server can be accessed within the data object, while for the fetch() method, the final data can be named any variable

Backward compatibility

One of the main selling points of Axios is its wide browser support. Even old browsers like IE11 can run Axios without any issues. This is because it uses XMLHttpRequest under the hood.

Fetch(), on the other hand, only supports Chrome 42+, Firefox 39+, Edge 14+, and Safari 10.3+ (you can see the full compatibility table on CanIUse.com).

If your only reason for using Axios is backward compatibility, you don’t need an HTTP library. Instead, you can use fetch() with a polyfill like this to implement similar functionality on web browsers that do not support fetch().

To begin using the fetch() polyfill, install it via the npm command like so:

npm install whatwg-fetch --save

Then, you can make requests like this:

import 'whatwg-fetch'
window.fetch(...)

Keep in mind that you might also need a promise polyfill in some old browsers.

Response timeout

The simplicity of setting a timeout in Axios is one of the reasons some developers prefer it to fetch(). In Axios, you can use the optional timeout property in the config object to set the number of milliseconds before the request is aborted.

For example:

axios({
  method: 'post',
  url: '/login',
  timeout: 4000,    // 4 seconds timeout
  data: {
    firstName: 'David',
    lastName: 'Pollock'
  }
})
.then(response => {/* handle the response */})
.catch(error => console.error('timeout exceeded'))

Fetch() provides similar functionality through the AbortController interface. It’s not as simple as the Axios version, though:

const controller = new AbortController();
const options = {
  method: 'POST',
  signal: controller.signal,
  body: JSON.stringify({
    firstName: 'David',
    lastName: 'Pollock'
  })
};  
const promise = fetch('/login', options);
const timeoutId = setTimeout(() => controller.abort(), 4000);

promise
  .then(response => {/* handle the response */})
  .catch(error => console.error('timeout exceeded'));

Here, we created an AbortController object using the AbortController.abort() constructor, which allows us to abort the request later. Signal is a read-only property of AbortController, providing a means to communicate with a request or abort it. If the server doesn’t respond in less than four seconds, controller.abort() is called, and the operation is terminated.

Automatic JSON data transformation

As we saw earlier, Axios automatically stringifies the data when sending requests (though you can override the default behavior and define a different transformation mechanism). When using fetch(), however, you’d have to do it manually.

Compare the two below:

// axios
axios.get('https://api.github.com/orgs/axios')
  .then(response => {
    console.log(response.data);
  }, error => {
    console.log(error);
  });

// fetch()
fetch('https://api.github.com/orgs/axios')
  .then(response => response.json())    // one extra step
  .then(data => {
    console.log(data) 
  })
  .catch(error => console.error(error));

Automatic transformation of data is a nice feature to have, but again, it’s not something you can’t do with fetch().

HTTP interceptors

One of the key features of Axios is its ability to intercept HTTP requests. HTTP interceptors come in handy when you need to examine or change HTTP requests from your application to the server or vice versa (e.g., logging, authentication, or retrying a failed HTTP request).

With interceptors, you won’t have to write separate code for each HTTP request. HTTP interceptors are helpful when you want to set a global strategy for how you handle requests and responses

Here’s how you can declare a request interceptor in Axios:

axios.interceptors.request.use(config => {
  // log a message before any HTTP request is sent
  console.log('Request was sent');

  return config;
});

// sent a GET request
axios.get('https://api.github.com/users/sideshowbarker')
  .then(response => {
    console.log(response.data);
  });

In this code, the axios.interceptors.request.use() method is used to define code to be run before an HTTP request is sent. Also, axios.interceptors.response.use() can be used to intercept the response from the server. Let’s say there is a network error; using the response interceptors, you can retry that same request using interceptors.

By default, fetch() doesn’t provide a way to intercept requests, but it’s not hard to come up with a workaround. You can overwrite the global fetch() method and define your interceptor, like this:

fetch = (originalFetch => {
  return (...arguments) => {
    const result = originalFetch.apply(this, arguments);
      return result.then(console.log('Request was sent'));
  };
})(fetch);

fetch('https://api.github.com/orgs/axios')
  .then(response => response.json())
  .then(data => {
    console.log(data) 
  });

Download progress

Progress indicators are very useful when loading large assets, especially for users with slow internet. Previously, JavaScript programmers used the XMLHttpRequest.onprogress callback handler to implement progress indicators.

The Fetch API doesn’t have an onprogress handler. Instead, it provides an instance of ReadableStream via the body property of the response object.

The following example illustrates the use of ReadableStream to provide users with immediate feedback during image download:

index.html
<!-- Wherever you html is -->
  <div id="progress" src="">progress</div>
  <img id="img">

script.js
'use strict'
const element = document.getElementById('progress');
fetch('https://fetch-progress.anthum.com/30kbps/images/sunrise-baseline.jpg')
  .then(response => {
    if (!response.ok) {
      throw Error(response.status+' '+response.statusText)
    }
    // ensure ReadableStream is supported
    if (!response.body) {
      throw Error('ReadableStream not yet supported in this browser.')
    }
    // store the size of the entity-body, in bytes
    const contentLength = response.headers.get('content-length');
    // ensure contentLength is available
    if (!contentLength) {
      throw Error('Content-Length response header unavailable');
    }
    // parse the integer into a base-10 number
    const total = parseInt(contentLength, 10);
    let loaded = 0;
    return new Response(
      // create and return a readable stream
      new ReadableStream({
        start(controller) {
          const reader = response.body.getReader();
          read();
          function read() {
            reader.read().then(({done, value}) => {
              if (done) {
                controller.close();
                return; 
              }
              loaded += value.byteLength;
              progress({loaded, total})
              controller.enqueue(value);
              read();
            }).catch(error => {
              console.error(error);
              controller.error(error)                  
            })
          }
        }
      })
    );
  })
  .then(response => 
    // construct a blob from the data
    response.blob()
  )
  .then(data => {
    // insert the downloaded image into the page
    document.getElementById('img').src = URL.createObjectURL(data);
  })
  .catch(error => {
    console.error(error);
  })
function progress({loaded, total}) {
  element.innerHTML = Math.round(loaded/total*100)+'%';
}

Implementing a progress indicator in Axios is simpler, especially if you use the Axios Progress Bar module. First, you need to include the following style and scripts:

// the head of your HTML
    <link rel="stylesheet" type="text/css"
        href="https://cdn.rawgit.com/rikmms/progress-bar-4-axios/0a3acf92/dist/nprogress.css" />


// the body of your HTML
     <img id="img" />
    <button onclick="downloadFile()">Get Resource</button>
    <script src="https://unpkg.com/axios/dist/axios.min.js"></script>
    <script src="https://cdn.rawgit.com/rikmms/progress-bar-4-axios/0a3acf92/dist/index.js"></script>

// add the following to customize the style

<style>
    #nprogress .bar {
        background: red !important;
    }
    #nprogress .peg {
        box-shadow: 0 0 10px red, 0 0 5px red !important;
    }
    #nprogress .spinner-icon {
        border-top-color: red !important;
        border-left-color: red !important;
    }
</style>

Then you can implement the progress bar like this:

    <script type="text/javascript">
        loadProgressBar();

        function downloadFile() {
          getRequest(
            "https://fetch-progress.anthum.com/30kbps/images/sunrise-baseline.jpg"
          );
        }

        function getRequest(url) {
          axios
            .get(url, { responseType: "blob" })
            .then(function (response) {
              const reader = new window.FileReader();
              reader.readAsDataURL(response.data);
              reader.onload = () => {
                document.getElementById("img").setAttribute("src", reader.result);
              };
            })
            .catch(function (error) {
              console.log(error);
            });
        }
      </script>

This code uses the FileReader API to asynchronously read the downloaded image. The readAsDataURL method returns the image’s data as a Base64-encoded string, which is then inserted into the src attribute of the img tag to display the image.

Simultaneous requests

To make multiple simultaneous requests, Axios provides the axios.all() method. Simply pass an array of requests to this method, then use axios.spread() to assign the properties of the response array to separate variables:

axios.all([
  axios.get('https://api.github.com/users/iliakan'), 
  axios.get('https://api.github.com/users/taylorotwell')
])
.then(axios.spread((obj1, obj2) => {
  // Both requests are now complete
  console.log(obj1.data.login + ' has ' + obj1.data.public_repos + ' public repos on GitHub');
  console.log(obj2.data.login + ' has ' + obj2.data.public_repos + ' public repos on GitHub');
}));

You can achieve the same result by using the built-in Promise.all() method. Pass all fetch requests as an array to Promise.all(). Next, handle the response by using an async function, like this:

Promise.all([
  fetch('https://api.github.com/users/iliakan'),
  fetch('https://api.github.com/users/taylorotwell')
])
.then(async([res1, res2]) => {
  const a = await res1.json();
  const b = await res2.json();
  console.log(a.login + ' has ' + a.public_repos + ' public repos on GitHub');
  console.log(b.login + ' has ' + b.public_repos + ' public repos on GitHub');
})
.catch(error => {
  console.log(error);
});

How to configure CORS

Cross-Origin Resource Sharing (CORS) is a mechanism available in HTTP to enable a server to permit the loading of its resources from any origins other than itself. For example, you need CORS when you want to pull data from external APIs that are public or authorized.

If the CORS mechanism is not properly enabled on the server, any request from a different server — regardless of whether or not it is made with Axios or fetch() — will receive the No Access-Control-Header-Present error.

To properly handle CORS, the first step is to configure the server, which depends on your environment/server. Once the server has been properly configured, it will automatically include the Access-Control-Allow-Origin header in response to all requests (see the documentation for more information).

A common error, in both Axios and fetch(), is to add the Access-Control-Allow-Origin to the request — this is a response parameter and is used by the server to specify the permitted access control for the origin.

Another aspect to be aware of, when you add the headers to your Axios request, is that the request is handled differently: the browser performs a preflight request before the actual request and this preflight request is an OPTIONS request that verifies if CORS is honored and if the actual request is safe to send the real request.

Effectively handling responses

Response management is a critical part of every application invoking an API. In this section, we will briefly look at the two aspects of it: getting the error code and manipulating response data.

Error management is different in Axios and fetch(). Specifically, fetch() doesn’t automatically reject the promise in the event of server-side errors, such as HTTP 404 or 500 status codes. This means that these errors do not trigger the .catch() block, unlike in Axios where such responses would typically be considered exceptions.

Instead, fetch() will resolve the promise normally with the ok status in the response set to false. The call to fetch() will only fail on network failures or if anything has prevented the request from completing.

In the following code, you can see how to handle errors in fetch():

 try {
  const res = await fetch('...');

  if (!res.ok) {
    // Error on the response (5xx, 4xx)
    switch (res.status) {
      case 400: /* Handle */ break;
      case 401: /* Handle */ break;
      case 404: /* Handle */ break;
      case 500: /* Handle */ break;
    }
  }

  // Here the response can be properly handled
} catch (err) {
    // Error on the request (Network error)
}

Meanwhile, in Axios, you can discriminate all errors in a proper catch block as shown in the following example:

try {
  let res = await axios.get('...');
  // Here the response can be properly handled
} catch (err) {
  if (err.response) {
    // Error on the response (5xx, 4xx)
  } else if (err.request) {
    // Error on the request (Network error)
  }
}

Once the request has been served with a proper response without any errors, you can handle the response payload that will be accessible by using two different mechanisms.

In fetch(), the request/response payload is accessible in the body field and must be stringified, while in Axios it is in the data field as a proper JavaScript object. This difference is captured in the two following stripped-down examples:

 // Using Fetch API
fetch('...')
  .then(response => response.json())
  .then(data => console.log(data))
  .catch(error => console.error('Error:', error)); 


 // Using Axios
axios.get('...')
  .then(response => console.log(response.data))
  .catch(error => console.error('Error:', error));

The key difference in fetch() lies in the use of the .json() method. Despite the name, this method does not produce JSON but instead, it will take JSON as input and parse it to produce a JavaScript object.

Conclusion

Axios provides an easy-to-use API in a compact package for most HTTP communication needs. However, if you prefer to stick with native APIs, nothing stops you from implementing Axios features.

As discussed in this article, it’s perfectly possible to reproduce the key features of the Axios library using the fetch() method provided by web browsers. Whether it’s worth loading a client HTTP API depends on whether you’re comfortable working with built-in APIs.

Axios	Fetch
Axios has url in request object.	Fetch has no url in request object.
Axios is a stand-alone third party package that can be easily installed.	Fetch is built into most modern browsers; no installation is required as such.
Axios enjoys built-in XSRF protection.	Fetch does not.
Axios uses the data property.	Fetch uses the body property.
Axios data contains the object.	Fetch’s body has to be stringified.
Axios request is ok when status is 200 and statusText is ‘OK’.	Fetch request is ok when response object contains the ok property.
Axios performs automatic transforms of JSON data.	Fetch is a two-step process when handling JSON data- first, to make the actual request; second, to call the .json() method on the response.
Axios allows cancelling request and request timeout.	Fetch does not.
Axios has the ability to intercept HTTP requests.	Fetch, by default, doesn’t provide a way to intercept requests.
Axios has built-in support for download progress.	Fetch does not support upload progress.
Axios has wide browser support.	Fetch only supports Chrome 42+, Firefox 39+, Edge 14+, and Safari 10.1+ (This is known as Backward Compatibility).
Axios “GET” call ignores data content	Fetch “GET” call can have body content