JSON - DataTypes

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There are following datatypes supported by JSON format:

TypeDescription
Numberdouble- precision floating-point format in JavaScript
Stringdouble-quoted Unicode with backslash escaping
Booleantrue or false
Arrayan ordered sequence of values
Valueit can be a string, a number, true or false, null etc
Objectan unordered collection of key:value pairs
Whitespacecan be used between any pair of tokens
nullempty

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 number types:

TypeDescription
IntegerDigits 1-9, 0 and positive or negative
FractionFractions like .3, .9
ExponentExponent 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:

TypeDescription
" 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 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.

  • Object 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 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;


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