JSON - DataTypes


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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;


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