What is JSON?

JSON stands for JavaScript Object Notation.

JSON is an open standard lightweight file format and data interchange format for storing and transporting data.

JSON is often used when data is sent from a server to a web page.

JSON is "self-describing" and easy to understand.

Advantages and why it is preferably used

• It is simple to build and debug.
• Low light-weight payload size.
• Acceptable across all modern high-level programming languages.

JSON Syntax Rules

• Data is in name and value pairs.
• A name/value pair consists of a field name (in double quotes), followed by a colon, followed by a value: [ "\"name\": \"John\"" ] (JSON names require double quotes).
• Data is separated by commas.
• Curly braces hold objects.
• Square brackets hold arrays.
• Arrays are called JSON Arrays.
• JSON Arrays hold JSON objects.
• JSON objects can contain other JSON objects and this is called Nested JSON Objects.

JSON Values

In JSON, values must be one of the following data types:

• string
• number
• object
• array
• boolean
• null

example is a JSON string

1{
2	"name": "John",
3	"age": 30,
4	"isMarried": false,
5	"car": null,
6	"hobbies": ["Hiking", "fishing", "cycling"],
7	"contactInfo": {
8		"phoneNumber": "000-000-000-000",
9		"address": "blah blah street, at something city, etc."
10	}
11}

JSON Files

The file type for JSON files is ".json" The MIME type for JSON text is "application/json"

JavaScript and JSON

JSON is a language-independent data format. It was derived from JavaScript (as it is syntactically identical to the code for creating JavaScript objects), So a JavaScript program can easily convert JSON data into native JavaScript objects. Many modern programming languages include code to generate and parse JSON-format data. JSON filenames use the extension [ ".json" ].

In JavaScript, an object value can be all like the values on JSON, plus any other valid JavaScript expression, including:

• function
• date
• undefined

Parsing JSON in JavaScript

Imagine we received this text from a web server:

[ "'{ \"name\": \"John\", \"age\": 30, \"isMarried\": false, \"car\": null, \"hobbies\": [\"Hiking\", \"fishing\", \"cycling\"], \"contactInfo\": { \"phoneNumber\": \"000-000-000-000\", \"address\": \"blah blah street, at something city etc.\" } }'" ]

Use the JavaScript function JSON.parse() to convert text into a JavaScript object:

1const data = JSON.parse(
2	'{ "name": "John", "age": 30, "isMarried": false, "car": null, "hobbies": ["Hiking", "fishing", "cycling"], "contactInfo": { "phoneNumber": "000-000-000-000", "address": "blah blah street, at something city etc." } }'
3);