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JSON (JavaScript Object Notation) is a lightweight data interchange format. It is easy for humans to read and write. It is easy for machines to parse and generate. JSON is a text format that is completely language-independent but uses conventions that are familiar to programmers of the C family of languages, including C, C++, C#, Java, JavaScript, Perl, Python, and many others. These properties make JSON an ideal data-interchange language. Let’s start 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
1 2 3 4 5 6 7 8 9 10 | var myObject = { "first": "John", "last": "Doe", "age": 39, "sex": "male", "salary": 70000, "registered": <span class="hljs-literal">true</span> }; |
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
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 | var myArray = [ { "first": "John", "last": "Doe", "age": 39, "sex": "male", "salary": 70000, "registered": <span class="hljs-literal">true</span> }, { "first": "Jane", "last": "Smith", "age": 42, "sex": "female", "salary": 80000, "registered": <span class="hljs-literal">true</span> }, { "first": "Amy", "last": "Burnquist", "age": 29, "sex": "female", "salary": 60000, "registered": <span class="hljs-literal">false</span> } ]; |
Access array elements
myArray[0] | returns { “first”: “John”, “last”: “Doe” … } |
myArray[1] | returns { “first”: “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
1 2 3 4 5 6 7 8 9 10 | var myArray = [ "John", "Doe", 39, "M", 70000, <span class="hljs-literal">true</span> ]; |
Access array elements
myArray[1] | returns “Doe” |
myArray[5] | returns true |
myArray[6] | returns undefined |
Nested objects and arrays
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 | var myObject = { "ref": { "first": 0, "last": 1, "age": 2, "sex": 3, "salary": 4, "registered": 5 }, "jdoe1": [ "John", "Doe", 39, "male", 70000, <span class="hljs-literal">true</span> ], "jsmith1": [ "Jane", "Smith", 42, "female", 80000, <span class="hljs-literal">true</span> ] }; |
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 |
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