Java Script Object Notation (JSON) is a data format that allows applications to communicate over networks in a simple syntax. JSON is used in Javascript (duh), Node.js, MongoDB (and other NoSQL databases).

Types of JSON documents

JSON documents can be the following two types:

Data Type Surrounding Characters Example
Array [] square brackets [ "Hello", "JSON" ]
Object {} curly braces {"Hello":"JSON"}

JSON Arrays

An array is simply a data structure with an ordering. All pairs except the last must be separated by commas



Objects are simply key value pairs, like the dictionary/map data structure. All keys must be unique, and all pairs except the last must be separated by commas.

   "myString" : "value",
   "nullValue": null,
   "myBoolean": true,
   "myNumber" : 0

JSON Schema

JSON Schema specifies the expected structure of JSON documents. This is used when a document must have a given structure, as in an API response.

Attached below is a fictitious programmer.json schema, outlining the valid format for a programmer object submitted to this API.

      "type": "object",
      "properties": {
              "firstName": { "type" : "string" },
              "lastName": { "type" : "string"},
              "age" : { "type" : "integer"},
              "editor" : {
                      "name" : { "type" : "string" },
                      "isVim" : { "type" : "boolean" }
              "projects" : { "type" : "array" }
      "required": ["firstName", "lastName", "editor"]

A valid programmer, aaron.json would be formatted as follows:

      "firstName" : "Aaron",
      "lastName" : "Cote",
      "age" : null,
      "editor" : {
              "name" :"Eclipse",
              "isVim" : false
      "projects": []