JavaScript JSON

What is JSON?

1. • JSON stands for JavaScript Object Notation
   • JSON is lightweight data interchange format
   • JSON is language independent *
   • JSON is "self-describing" and easy to understand
   * The JSON syntax is derived from JavaScript object notation syntax, but the JSON format is text only. Code for reading and generating JSON data can be written in any programming language.

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   JSON Example

   This JSON syntax defines an employees object: an array of 3 employee records (objects):

   JSON Example

   {
   "employees":[
       {"firstName":"John", "lastName":"Doe"}, 
       {"firstName":"Anna", "lastName":"Smith"},
       {"firstName":"Peter", "lastName":"Jones"}
   ]
   }
   

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   The JSON Format Evaluates to JavaScript Objects

   The JSON format is syntactically identical to the code for creating JavaScript objects.
   Because of this similarity, a JavaScript program can easily convert JSON data into native JavaScript objects.

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   JSON Syntax Rules

• Data is in name/value pairs
• Data is separated by commas
• Curly braces hold objects
• Square brackets hold arrays

Converting a JSON Text to a JavaScript Object

A common use of JSON is to read data from a web server, and display the data in a web page.

For simplicity, this can be demonstrated using a string as input.

First, create a JavaScript string containing JSON syntax:

var text = '{ "employees" : [' +
'{ "firstName":"John" , "lastName":"Doe" },' +
'{ "firstName":"Anna" , "lastName":"Smith" },' +
'{ "firstName":"Peter" , "lastName":"Jones" } ]}';

Then, use the JavaScript built-in function JSON.parse() to convert the string into a JavaScript object:

var obj = JSON.parse(text);

Finally, use the new JavaScript object in your page:

Example

<p id="demo"></p>

<script>
document.getElementById("demo").innerHTML =
obj.employees[1].firstName + " " + obj.employees[1].lastName;</script>