JSON - DataTypes

JSON format supports the following data types −

Number

It is a double precision floating-point format in JavaScript and it depends on implementation.

Octal and hexadecimal formats are not used.

No NaN or Infinity is used in Number.

The following table shows the number types −

Syntax

var json-object-name = { string : number_value, .......}

Example

Example showing Number Datatype, value should not be quoted −

var obj = {marks: 97}

String

It is a sequence of zero or more double quoted Unicode characters with backslash escaping.

Character is a single character string i.e. a string with length 1.

The table shows various special characters that you can use in strings of a JSON document −

Syntax

var json-object-name = { string : "string value", .......}

Example

Example showing String Datatype −

var obj = {name:  Amit }

Boolean

It includes true or false values.

Syntax

var json-object-name = { string : true/false, .......}

Example

var obj = {name:  Amit , marks: 97, distinction: true}

Array

It is an ordered collection of values.

These are enclosed in square brackets which means that array begins with .[. and ends with .]..

The values are separated by , (comma).

Array indexing can be started at 0 or 1.

Arrays should be used when the key names are sequential integers.

Syntax

[ value, .......]

Example

Example showing array containing multiple objects −

{
   "books": [
      { "language":"Java" , "edition":"second" },
      { "language":"C++" , "lastName":"fifth" },
      { "language":"C" , "lastName":"third" }
   ]
}

Object

It is an unordered set of name/value pairs.

Objects are enclosed in curly braces that is, it starts with { and ends with } .

Each name is followed by : (colon) and the key/value pairs are separated by , (comma).

The keys must be strings and should be different from each other.

Objects should be used when the key names are arbitrary strings.

Syntax

{ string : value, .......}

Example

Example showing Object −

{
   "id": "011A",
   "language": "JAVA",
   "price": 500,
}

Whitespace

It can be inserted between any pair of tokens. It can be added to make a code more readable. Example shows declaration with and without whitespace −

Syntax

{string:" ",....}

Example

var obj1 = {"name": "Sachin Tendulkar"}
var obj2 = {"name": "SauravGanguly"}

null

It means empty type.

Syntax

null

Example

var i = null;

if(i == 1) {
   document.write("<h1>value is 1</h1>");
} else {
   document.write("<h1>value is null</h1>");
}

JSON Value

It includes −

number (integer or floating point)

string

boolean

array

object

null

Syntax

String | Number | Object | Array | TRUE | FALSE | NULL

Example

var i = 1;
var j = "sachin";
var k = null;