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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
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number
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var myNum = 123.456;
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Series of numbers; decimals ok; double-precision floating-point format
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string
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var myString = “abcdef”;
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Series of characters (letters, numbers, or symbols); double-quoted UTF-8 with backslash escaping
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boolean
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var myBool = true;
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true or false
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array
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var myArray = [ “a”, “b”, “c”, “d” ];
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sequence of comma-separated values (any data type); enclosed in square brackets
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object
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var myObject = { “id”: 7 };
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unordered collection of comma-separated key/value pairs; enclosed in curly braces; properties (keys) are distinct strings
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null
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var myNull = null;
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variable with null (empty) value
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undefined
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var myUndefined;
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variable with no value assigne
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Objects
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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
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myObject.sex
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returns “male”
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myObject[”age”]
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returns 39
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myObject[0]
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returns “John”
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myObject.something
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returns undefined
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myObject[6]
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returns undefined
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Array of objects
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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
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myArray[0]
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returns { “first”: “John”, “last”: “Doe” … }
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myArray[1]
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returns { “first”: “Jane”, “last”: “Smith” … }
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myArray[1].first
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returns “Jane”
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myArray[1][2]
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returns 42
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myArray[2].registered
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returns false
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myArray[3]
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returns undefined
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myArray[3].sex
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error: “cannot read property…”
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Arrays
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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
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myArray[1]
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returns “Doe”
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myArray[5]
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returns true
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myArray[6]
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returns undefined
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Nested objects and arrays
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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
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myObject.ref.first
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returns 0
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myObject.jdoe1
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returns [ “John”, “Doe”, 39 … ]
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myObject[2]
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returns [ “Jane”, “Smith”, 42 … ]
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myObject.jsmith1[3]
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returns “female”
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myObject[1][5]
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returns true
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myObject.jdoe1[myObject.ref.last]
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returns “Doe”
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myObject.jsmith1[myObject.ref.age]
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returns 42
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