JSON Introduction

What is JSON?

•  JSON stands for JavaScript Object Notation.
•  JSON is lightweight text-data interchange format.
•  JSON is language independent.
•  JSON is "self-describing" and easy to understand.

JSON uses JavaScript syntax for describing data objects, but JSON is still language and platform independent. JSON parsers and JSON libraries exists for many different programming languages.

JSON format is a format similar to XML but usually it is shorter and easier to parse. Many web services now work with JSON. Using the new JSON library, you can parse and generate JSON strings easily.

Much like XML

• JSON is plain text
• JSON is "self-describing" (human readable)
• JSON is hierarchical (values within values)
• JSON can be parsed by JavaScript
• JSON data can be transported using AJAX

Much Unlike XML

• No end tag
• Shorter
• Quicker to read and write
• Can be parsed using built-in JavaScript eval()
• Uses arrays
• No reserved words

Why JSON?

For AJAX applications, JSON is faster and easier than XML:

Using XML

• Fetch an XML document
• Use the XML DOM to loop through the document
• Extract values and store in variables

Using JSON

• Fetch a JSON string
• eval() the JSON string

GSM, 3G, Edge, WIFI, GPS

GSM: (Global System for Mobile Communications: originally from Groupe Spécial Mobile) is the most popular standard for mobile.


3G stands: for 3rd-generation mobile technology. The services associated with 3G provide the ability to transfer both voice data and non-voice data. 3G brings wireless transmission speeds, which allow full motion video, high-speed internet access and video-conferencing. 


Edge means: Enhanced Data rates for GSM Evolution (EDGE) is a digital mobile phone technology which acts as a bolt-on enhancement to 2G and 2.5G GPRS networks. It can carry data speeds up to 384 kbit/s in packet mode and will therefore meet the International Telecommunications Union's requirement for a 3G network.

WIFI:  wireless local area network: a local area network that uses high frequency radio signals to transmit and receive data over distances of a few hundred feet; uses ethernet protocol)

GPS: (a navigational system involving satellites and computers that can determine the latitude and longitude of a receiver on Earth by computing the time difference for signals from different satellites to reach the receiver)

Should variables be stored in local blocks?

The use of local blocks for storing variables is unusual and therefore should be avoided, with only rare exceptions. One of these exceptions would be for debugging purposes, when you might want to declare a local instance of a global variable to test within your function. You also might want to use a local block when you want to make your program more readable in the current context.

Sometimes having the variable declared closer to where it is used makes your program more readable. However, well-written programs usually do not have to resort to declaring variables in this manner, and you should avoid using local blocks.