JavaScript: JSON

By Xah Lee. Date: . Last updated: .

JSON is the value of the property key "JSON" of the Global Object.

console.log( window["JSON"] === JSON ); // true

Type

Type of JSON is Object .

console.log( typeof JSON === "object" ); // true

console.log( Object.prototype.toString.call( JSON ) === "[object JSON]" ) // true

Parent

Parent of JSON is Object.prototype. [see Prototype and Inheritance]

console.log( Reflect.getPrototypeOf ( JSON ) === Object.prototype ); // true

Purpose

Purpose of JSON is as a namespace, for functions working with the JSON data interchange format.

What's JSON Data Interchange Format?

JSON is a data interchange format.

JSON is a more strict syntax of nested JavaScript object or array. Used to pass data to the web browser, or exchange data with other language, API.

For example, here's a JSON:

{
  "firstName": "John",
  "lastName": "Smith",
  "isAlive": true,
  "age": 25,
  "address": {
    "streetAddress": "21 2nd Street",
    "city": "New York",
    "state": "NY",
    "postalCode": "10021-3100"
  },
  "phoneNumbers": [
    {
      "type": "home",
      "number": "212 555-1234"
    },
    {
      "type": "office",
      "number": "646 555-4567"
    }
  ],
  "children": [],
  "spouse": null
}

JavaScript Syntax vs JSON Syntax

JSON syntax is more strict than JavaScript syntax. For example:

{h:2}
bad. JSON does not allow unquoted property key.
{'h':2}
bad. JSON does not allow single quote.
{"h":2,}
bad. JSON does not allow extra comma at end.
[undefined]
bad. JSON value does not allow undefined. (but null is ok)

Properties

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