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)

Parsing JSON data


Now that we are familiar with jQuery, let us trigger an AJAX request on an event such as a button click.

In this snippet, let us begin by observing the HTML document object. We have a div element that has an empty unordered list. The aim of this script is to populate the unordered list with list items on the click of a button. The input button element has an id with the value "getFeed", and the click event handler will be tied to this button. Since AJAX is asynchronous and as we are tying a callback to this button, no AJAX calls are made to our live server when the document object is loaded. The HTML structure alone is loaded onto the page, and the events are tied to these elements.

When the button is clicked on, we are using the method getJSON to make an AJAX call to the live web server to retrieve the JSON data. Since we are getting an array of students, we will pass the retrieved data into jQuerys' each iterator to retrieve one element at a time. Inside the iterator, we...