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 −

• 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;