JSON Cheat Sheet

A JSON cheat sheet.

Data Types

number	var myNum = 123.456;	Series of numbers; decimals ok; double-precision floating-point format
string	var myString = “ abcdef” ;	Series of characters (letters, numbers, or symbols); double-quoted UTF-8 with backslash escaping
boolean	var myBool = true;	true or false
array	var myArray = [ “ a” , “ b” , “ c” , “ d” ];	sequence of comma-separated values (any data type); enclosed in square brackets
object	var myObject = { “ id” : 7 };	unordered collection of comma-separated key/value pairs; enclosed in curly braces; properties (keys) are distinct strings
null	var myNull = null;	variable with null (empty) value
undefined	var myUndefined;	variable with no value assigne

Objects

var myObject = {
“ first” : “ John” ,
“ last” : “ Doe” ,
“ age” : 39,
“ sex” : “ male” ,
“ salary” : 70000,
“ registered” : true
};

Access object properties

myObject. sex	returns “ male”
myObject[” age” ]	returns 39
myObject[0]	returns “ John”
myObject. something	returns undefined
myObject[6]	returns undefined

Array of objects

var myArray = [
{
“ first” : “ John” ,
“ last” : “ Doe” ,
“ age” : 39,
“ sex” : “ male” ,
“ salary” : 70000,
“ registered” : true
},
{
“ first” : “ Jane” ,
“ last” : “ Smith” ,
“ age” : 42,
“ sex” : “ female” ,
“ salary” : 80000,
“ registered” : true
},
{
“ first” : “ Amy” ,
“ last” : “ Burnquist” ,
“ age” : 29,
“ sex” : “ female” ,
“ salary” : 60000,
“ registered” : false
}
];

Access array elements

myArray[0]	returns { “ fist” : “ John” , “ last” : “ Doe” … }
myArray[1]	returns { “ fist” : “ Jane” , “ last” : “ Smith” … }
myArray[1]. first	returns “ Jane”
myArray[1][2]	returns 42
myArray[2]. registered	returns false
myArray[3]	returns undefined
myArray[3]. sex	error: “ cannot read property… ”

Arrays

var myArray = [
“ John” ,
“ Doe” ,
39,
“ M” ,
70000,
true
];

Access array elements

myArray[1]	returns “ Doe”
myArray[5]	returns true
myArray[6]	returns undefined

Nested objects and arrays

var myObject = {
“ ref” : {
“ first” : 0,
“ last” : 1,
“ age” : 2,
“ sex” : 3,
“ salary” : 4,
“ registered” : 5
},
“ jdoe1” : [
“ John” ,
“ Doe” ,
39,
“ male” ,
70000,
true
],
“ jsmith1” : [
“ Jane” ,
“ Smith” ,
42,
“ female” ,
80000,
true
]
};

Access nested elements

myObject. ref. first	returns 0
myObject. jdoe1	returns [ “ John” , “ Doe” , 39 … ]
myObject[2]	returns [ “ Jane” , “ Smith” , 42 … ]
myObject. jsmith1[3]	returns “ female”
myObject[1][5]	returns true
myObject. jdoe1[myObject. ref. last]	returns “ Doe”
myObject. jsmith1[myObject. ref. age]	returns 42