JSON DataTypes

JSON format supports the following data types −

Type

Description

Number

double- precision floating-point format in JavaScript

String

double-quoted Unicode with backslash escaping

Boolean

true or false

Array

an ordered sequence of values

Value

it can be a string, a number, true or false, null etc

Object

an unordered collection of key:value pairs

Whitespace

can be used between any pair of tokens

null

empty

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 −

Type

Description

Integer

Digits 1-9, 0 and positive or negative

Fraction

Fractions like .3, .9

Exponent

Exponent like e, e+, e-, E, E+, E-

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 string types −

Type

Description

"

double quotation

\

reverse solidus

/

solidus

b

backspace

f

form feed

n

new line

r

carriage return

t

horizontal tab

u

four hexadecimal digits

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 name/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 i = " sachin";

var j = " saurav"

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 −

Syntax

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

Example

var i = 1;

var j = "sachin";

var k = null;