Basic Guide

What is JSON?

What is JSON?

JSON (JavaScript Object Notation) is a type of notation used for expressing structured data. BLOCKS uses data expressed in JSON in many situations.

This document is intended for those unfamiliar with JSON and only covers the basics required for using JSON in BLOCKS. For a more detailed explanation, please refer to Introducing JSON and RFC 7159 .

Example JSON data

Consider the profile information shown below:

What is JSON?: sample data

The following is an example of expressing that information in JSON:

{"name":"John Smith","age":35,"languages":["English","Japanese"]}

You can also use line breaks and spaces to make JSON easier to read.

{
 "name": "John Smith",
 "age": 35,
 "languages": ["English", "Japanese"]
}

Both examples express the same data.

In JSON, you write data as a collection of “name” and “value” pairs. For our profile example, the pair "age": 35 has the name "age" and the value 35.

We refer to data expressed in JSON as JSON text.

Writing JSON

The types of data (values) that can be expressed using JSON are as follows: strings, numbers, arrays, objects, and literal names (true, false, null).

Value type Explanation
String Characters contained within a set of double quotation marks ("). Example: "John Smith"
Number Numbers represented in base 10. Scientific notation can also be used. Examples: 35, 1.234e-5
Array Multiple values separated by commas (,) and contained within square brackets ([ and ]) Each value within an array is called an element. Example: ["English", "Japanese"]
Object

Multiple name and value pairs.

  • Pairs are separated by commas (,) and contained within curly brackets ({ and }). Example: {"name":"John Smith","age":35,"languages":["English","Japanese"]}
  • The name and value of a pair are separated by a colon (name: value).
  • Names are expressed as strings (enclosed in ")
  • A name and value pair is called a member.
true Boolean true. true must be written in all lower-case characters.
false Boolean false. false must be written in all lower-case characters.
null Expresses that the value is empty. null must be written in all lower-case characters.

In JSON, these values are combined to express data as shown in Example JSON data.