JSON - DataTypes

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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;