
When AJAX came to the modern web, it changed the definition of how web works. We all are using ajax for a long time but not with Fetch API. To load a new content in a web page, we do not need a full page reload. Using AJAX, we can post or pull data from a web server asynchronously.
Almost every web application nowadays use ajax. It was all possible because of the XMLHttpRequest. It is a browser API in the form of an object whose methods transfer data between a web browser and a web server. The object is provided by the browser’s JavaScript environment.
Our one of the most popular JavaScript libraries, jQuery uses XMLHttpRequest to make HTTP calls. If we talk about any networking library in any modern JavaScript ecosystem uses XMLHttpRequest like axios (promise-based), superagent (callback-based).
The issues with XMLHttpRequest
Making HTTP request with raw XMLHttpRequest really sucks. You need to take care a lot of things to get some data from the server. To make a get request with XMLHttpRequest, we need to write the code like
var xhr = new XMLHttpRequest(); xhr.onreadystatechange = function() { if (xhr.readyState == XMLHttpRequest.DONE) { alert(xhr.responseText); } } xhr.open('GET', 'http://example.com', true); xhr.send(null);
We tend to use jQuery’s Ajax (84 KB). If in a web application, we are adding jQuery to make only a few requests, then It is not at all bandwidth friendly. We are loading a script of 84kb to use only one or two methods. The problem can be solved using the Fetch API which is already present in our browser.
Introduction to Fetch API
Fetch is a promise based HTTP networking API provided by the browser. It is here from the chrome 42. Firefox also supports it. It is now almost standardised. It saves you from remembering complex API of XMLHttpRequest. Look at one example of Fetch.
fetch('some/api/getData.json') .then( function(response) { if (response.status !== 200) { console.log('Status Code: ' + response.status); return; } response.json().then(function(data) { console.log(data); }); } ) .catch(function(err) { console.log(err); });
It is clean. It is excellent. Here we are making a simple get request. Fetch always returns a promise. Promise resolves to the response object. This response object has different helper methods like response.json(), response.text(), response.blob() etc.
Usage of Fetch
It can fully replace old XMLHttpRequest. The first parameter of the fetch is the requested URL. We can also pass a second parameter which is essentially a configuration object. In this configuration object, we can specify different options like HTTP Method Type, Headers of the Request, body of the request etc. Let’s look at how to make a post request with Fetch.
Post Request using Fetch API
function json(response) { return response.json() } var url = '/api/saveData'; fetch(url, { method: 'post', headers: { "Content-type": "application/x-www-form-urlencoded" }, body: 'foo=bar&lorem=ipsum&[email protected]' }) .then(json) .then(function (data) { console.log(data); }) .catch(function (error) { console.log('Failed', error); });
Here we are chaining our response through our json method. The code is self-explanatory.
If you are yet not convinced to use Fetch. There is an excellent fetch polyfill library that you can try.
We will encourage you to use fetch over XMLHttpRequest in your next vanilla JavaScript project.

Janeth Kent
Licenciada en Bellas Artes y programadora por pasión. Cuando tengo un rato retoco fotos, edito vídeos y diseño cosas. El resto del tiempo escribo en MA-NO WEB DESIGN AND DEVELOPMENT.
Related Posts
How to use the endsWith method in JavaScript
In this short tutorial, we are going to see what the endsWith method, introduced in JavaScript ES6, is and how it is used with strings in JavaScript. The endsWith method is…
What are javascript symbols and how can they help you?
Symbols are a new primitive value introduced by ES6. Their purpose is to provide us unique identifiers. In this article, we tell you how they work, in which way they…
Callbacks in JavaScript
Callback functions are the same old JavaScript functions. They have no special syntax, as they are simply functions that are passed as an argument to another function. The function that receives…
How to create PDF with JavaScript and jsPDF
Creating dynamic PDF files directly in the browser is possible thanks to the jsPDF JavaScript library. In the last part of this article we have prepared a practical tutorial where I…
How to make your own custom cursor for your website
When I started browsing different and original websites to learn from them, one of the first things that caught my attention was that some of them had their own cursors,…
Node.js and npm: introductory tutorial
In this tutorial we will see how to install and use both Node.js and the npm package manager. In addition, we will also create a small sample application. If you…
How to connect to MySQL with Node.js
Let's see how you can connect to a MySQL database using Node.js, the popular JavaScript runtime environment. Before we start, it is important to note that you must have Node.js installed…
JavaScript Programming Styles: Best Practices
When programming with JavaScript there are certain conventions that you should apply, especially when working in a team environment. In fact, it is common to have meetings to discuss standards…
Difference between arrow and normal functions in JavaScript
In this tutorial we are going to see how arrow functions differ from normal JavaScript functions. We will also see when you should use one and when you should use…
JavaScript Arrow functions: What they are and how to use them
In this article we are going to see what they are and how to use JavaScript Arrow Functions, a new feature introduced with the ES6 standard (ECMAScript 6). What are Arrow…
How to insert an element into an array with JavaScript
In this brief tutorial you will learn how to insert one or more elements into an array with JavaScript. For this we will use the splice function. The splice function will not…
What is the difference between primitives types and objects in JavaScript?
In this short tutorial we are going to look at the differences between primitive types and objects in JavaScript. To start with, we're going to look at what primitive types…