Javascript Object Notation (JSON) is a lightweight data-interchange language. 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.

JSON can be written in two forms:

• Object - a collection of name-value pairs enclosed in curly brackets {}.
• Array - an ordered list of values enclosed in square brackets [].

Below is a basic example of a name-value pair.

"name":"Adam"

A name-value pair cannot be enclosed in single quotes, double quotes must be used.

'name':'Adam'

Multiple name-value pairs must be seperated by commas.

"firstName":"Adam", 
"lastName":"Banks", 
"age":28

The complete syntax of a JSON object includes a pair of curly brackets.

{ "name":"Adam" }

The complete syntax of a JSON array includes a pair of square brackets.

[ "Adam","Abel","Alex" ]

The following are the JSON data types:

• Object (JSON Object)
• String
• Number
• Boolean
• Array
• Null

As mentioned before, JSON object must be enclosed in curly braces.

{ "name":"Adam" }

An example of multiple name-value pairs.

{
  "firstName":"Adam", 
  "lastName":"Banks", 
  "age":28
}

JSON Values can also be objects.

{ "student":{ "name":"Adam" } }

{
  "student": {
  "firstName":"Adam", 
  "lastName":"Banks", 
  "age":28
  }
}

As we have seen above, JSON Values can be a string, "this is a string".
In addition, the following characters must be escaped with a backslash \ when used in a JSON string:

• \" (double quotes)
• \\ (backslash)
• \/ (forward slash)
• \b (backspace)
• \f (form feed)
• \t (tab)
• \n (new line)
• \r (carriage return)
• \u followed by hexadecimal characters (e.g. the smiley emoticon \u263A)

{ "description":"the ship was named \"hero of the sea\" by vote! \u263A" }

JSON Values can be positive or negative numbers without the quotes.

• Integers
• Decimals
• Exponents

{
  "quantity": 13,
  "price": 5.99,
  "latitude": 42.210345,
  "longitude": -118.894329,
  "speed": 2.998E+8
}

JSON Values can be true or false all lowercase, and without the quotes.

{
  "name":"Adam Banks",
  "age":28,
  "employed":false,
  "married":true
}

JSON Values can be Arrays. This is a list of any of the JSON data types, object, string, number, array, boolean or null. All the Values in an Array must be of the same data type.

{
  "name":"Adam Banks",
  "age":28,
  "children": [ 
    "Mike", 
    "Ari", 
    "Luna" 
  ]
}

JSON Values can be null, all lowercase, and without the quotes.

{
  "name":"Adam Banks",
  "age":28,
  "children": null
}

JSON Schema is a vocabulary that allows you to annotate and validate JSON documents. The list of data types available in JSON leads to all kinds of data representation.

This is where the JSON Schema comes in, it allows you to define what is valid and acceptable in your JSON document. The key features include:

• Describes your existing data format(s).
• Provides clear human- and machine- readable documentation.
• Validates data which is useful for:
  • Automated testing.
  • Ensuring quality of client submitted data.

The JSON document being validated or described is called the instance, and the document containing the validation description is called the schema.

The most basic schema is a blank JSON object. This accepts anything, as long as it’s valid JSON

{}

You can also use true in place of {} to represent a schema that matches anything, or the oppositefalse for a schema that matches nothing.

true

false

Here is a complete example of a schema document:

{
  "$id": "https://your-domain.com/example.schema.json",
  "$schema": "http://json-schema.org/schema#",
  "title": "Student Record",
  "description": "Validating a student record.",
  "type": "object",
  "required": [ "firstName", "lastName", "age", "email" ],
  "properties": {
    "firstName": {
      "type": "string",
      "minLength": 2,
      "maxLength": 50
    },
    "lastName": {
      "type": "string",
      "minLength": 2,
      "maxLength": 50
    },
    "middleName": {
      "type": "string",
      "minLength": 2,
      "maxLength": 50
    },
    "age": {
      "type": "number",
      "minimum": 18,
      "maximum": 180
    },
    "email": {
      "type": "string",
      "pattern": "^[a-z0-9_-]+(\\.[_a-z0-9]+)*@[a-z0-9-]+(\\.[a-z0-9-]+)*(\\.[a-z]{2,10})$"
    },
    "married": {
      "type": "boolean"
    }
  }
}

All documentation on this page is taken from JSON.org and JSON-Schema.org