Using HTML 5 Fetch API to consume JSON

I have split the front end app from backend Rails API app in my current project. I was looking for simple way to interact with a remote server and consume JSON. HTML 5 includes a Fetch API that we can use. In this article, we will see how to make a post request using the Fetch API. Install node. Before upgrade I had:

$ node -v
$ npm -v

After upgrade:

$ node -v
$ npm -v

Install a simple Node HTTP server

npm install http-server -g

Start the local server:


You can install live-server if you want the browser to refresh automatically when the file is saved. Here is a simple GET request using the Fetch API:

    .then(response => response.json())
    .then(json => console.log(json))

Here is the POST request:

fetch('', {  
    method: 'POST',  
    body: JSON.stringify({
    title: 'testing post',
    body: 'did you get it',
.then(function (data) {  
  console.log('Request success: ', data);  
.catch(function (error) {  
  console.log('Request failure: ', error);  

Let's take the user filled out form and submit to the server:

<!DOCTYPE html>
    <title>Fetch POST example</title>
  <body class="container">
  <form method="POST" action="" id="form">
      Title: <input type="text" name="title" id='title'/>
      Body <textarea id="body" class="form-control" name='body' rows="5"></textarea>
      <button type="submit">Submit</button>

  <div id="results"></div>
      var formEl = document.getElementById('form');
      formEl.addEventListener('submit', function(event) {
        // 1. Setup the request
        // ================================
        // 1.1 Headers
        var headers = new Headers();
        // Tell the server we want JSON back
        headers.set('Accept', 'application/json');
        // 1.2 Form Data
        // We need to properly format the submitted fields.
        // Here we will use the same format the browser submits POST forms.
        // You could use a different format, depending on your server, such
        // as JSON or XML.
        var formData = new FormData();
        for (var i = 0; i < formEl.length; ++i) {
          formData.append(formEl[i].name, formEl[i].value);
        // This is for the purpose of this demo using jsFiddle AJAX Request endpoint
        var title = document.getElementById('title').value;
        var body = document.getElementById('body').value;

        formData.append('json', JSON.stringify({title: 'title', body: 'body'}));
        // 2. Make the request
        // ================================
        var url = '';
        var fetchOptions = {
          method: 'POST',
          body: formData
        var responsePromise = fetch(url, fetchOptions);
        // 3. Use the response
        // ================================
            // 3.1 Convert the response into JSON-JS object.
          .then(function(response) {
            return response.json();
          // 3.2 Do something with the JSON data
          .then(function(jsonData) {
            document.getElementById('results').innerText =

It took me a few hours to get this to work by putting bits and pieces from different resources into one working example. I hope you find this helpful.


Simple Fetch API Post example
Google Developers Fetch API
JS Fiddle Example

Related Articles

Ace the Technical Interview

  • Easily find the gaps in your knowledge
  • Get customized lessons based on where you are
  • Take consistent action everyday
  • Builtin accountability to keep you on track
  • You will solve bigger problems over time
  • Get the job of your dreams

Take the 30 Day Coding Skills Challenge

Gain confidence to attend the interview

No spam ever. Unsubscribe anytime.