Book Image

JavaScript and JSON Essentials

By : Sai S Sriparasa
Book Image

JavaScript and JSON Essentials

By: Sai S Sriparasa

Overview of this book

The exchange of data over the Internet has been carried out since its inception. Delimiter-separated lists such as CSV and tag-separated languages such as XML are very popular, yet they are considered to be verbose by a section of developers. JSON (JavaScript Object Notation) is a lightweight text-based code to create objects to transfer data over the Internet. It is a data exchange format that is human-readable (like XML, but without the markup around your actual payload) and its syntax is a subset of the JavaScript language that was standardized in 1999. JavaScript and JSON Essentials is a step-by-step guide that will introduce you to JSON and help you understand how the lightweight JSON data format can be used in different ways either to store data locally or to transfer data over the Internet. This book will teach you how to use JSON effectively with JavaScript. This book begins with a brief refresher course on JavaScript before taking you through how JSON data can be transferred via synchronous, asynchronous, and cross-domain asynchronous HTTP calls. JSON is not just about data transfer; this book throws light on the alternate implementations of JSON as well. You will learn the data types that JavaScript uses and how those data types can be used in JSON. You will go through the concepts of how to create, update, parse, and delete a JSON object. You will also look at the different techniques of loading a JSON file onto a web page, how to use jQuery to traverse through an object, and how to perform access operations. You will also go over a few resources that will make debugging JSON quick and easy.
Table of Contents (15 chapters)

Making your first AJAX call

Now that we have an active JSON data feed, it is about time to make our first AJAX call. We will look at two approaches of making an AJAX call; these approaches come from different periods in time. The first approach will use basic JavaScript so that we understand what happens behind the scenes when an AJAX call is made. Once we understand the concept of AJAX, we will use a popular JavaScript library to make the same AJAX call but with simpler code. Let's take a look at our first approach using basic JavaScript:

We will begin with our basic index.html file that loads an external JavaScript file. This JavaScript file performs the AJAX call to fetch the students JSON feed.

Let us take a look at index.js:

This is the original way in which an AJAX call is made to a live web server; let's break this script into pieces and investigate it piece by piece:

In the preceding snippet we are creating an instance of the XMLHttpRequest object. The XMLHttpRequest object lets us make...