JSON
In this chapter you will learn:
- What is JSON
- What is JSON Syntax
- How to use JSON to represent simple values
- How to use JSON to represent objects
- How to use JSON to represent arrays
What is JSON
JSON stands for JavaScript Object Notation. It uses JavaScript to represent structured data. JSON is a data format, not a programming language.
JSON Syntax
JSON syntax allows the representation of three types of values:
| Value | Description |
|---|---|
| Simple Values | Strings, numbers, Booleans, and null can be represented in JSON using the same syntax as JavaScript. undefined is not supported. |
| Objects | represent ordered key-value pairs. Each value may be a primitive type or a complex type. |
| Arrays | represent an ordered list of values that are accessible by a numeric index. The values may be simple values, objects, and other arrays. |
There are no variables, functions, or object instances in JSON.
Simple Values
In its simplest form, JSON represents a small number of simple values. For example, the following is valid JSON:
5
The following is an valid JSON representing a string:
"Hello world"
JSON strings must use double quotes.
Objects
Object literals in JavaScript look like this:
var tutorial = {
name: "JavaScript",
page: 9
};
The JSON representation of this same object is:
{
"name": "JavaScript",
"page": 9
}
There is no trailing semicolon. The quotes around the property name are required. The value can be any simple or complex value:
{ //from ja va2 s . c o m
"name": "JavaScript",
"page": 9,
"topic": {
"name": "Data Type",
"content": "Number"
}
}
Arrays
Arrays are represented in JSON using array literal notation from JavaScript. For example, this is an array in JavaScript:
var values = [1, "JavaScript", true];
You can represent this same array in JSON using a similar syntax:
[1, "JavaScript", true]
Arrays and objects can be used together to represent more complex collections of data, such as:
[/*from j av a 2 s . c o m*/
{
"title": "JavaScript",
"authors": ["J"],
edition: 3,
year: 2011
},
{
"title": "HTML",
"authors": [ "H" ],
edition: 2,
year: 2009
},
{
"title": "Ajax",
"authors": ["X", "Y", "Z" ],
edition: 2,
year: 2008
},
{
"title": "CSS",
"authors": ["A", "B", "C" ],
edition: 1,
year: 2007
},
{
"title": "Java",
"authors": ["C"],
edition: 1,
year: 2006
}
]
Next chapter...
What you will learn in the next chapter:
- Create JSON object from string
- How to use JSON.parse() to create JSON object
- How to control and use the parsing options in JSON parsing