JSON Syntax

JSON syntax is derived from JavaScript object notation syntax.

- Data is in name/value pairs (, )
- Curly braces hold objects where name is followed by :(colon)({ : })
- Data is separated by commas { : , : }
- Square brackets hold arrays and values are separated by comma (,). the values can also be an object. [ , ]

JSON vs Javascript Objects

The JSON format looks similar to JavaScript objects.

JSON vs JS Keys/ Name

JSON

The only difference is in JSON, keys must be strings, written within double quotes.

{ "name": "John" }

JavaScript

In JavaScript, keys can be strings, numbers, or identifier names.

{ name:"John" }

JSON vs JS Values

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

- an object (JSON object)
- a string
- a number
- an array
- a boolean
- null

In JavaScript values can be all of the above and also other valid JavaScript expression like below.

- a function
- a date
- undefined

String Values

In JSON, string values must be written with double quotes:

JSON

{ "name":"John" }

In JavaScript, you can write string values with double or single quotes:

JavaScript

{ name:'John' }

Accesing JSON data

Since JSON syntax is derived from JavaScript object notation you can access the json data similar way as we access javascript objects.

Below is an example to access data from the javascript object.

Example

var person = { "name":"David", "age":32, "city":"California" };

You can access a JavaScript object like this.

// returns John
person.name;
OR
// returns John
person["name"];

Modifying Data

person.name = "Gilbert";
OR
person["name"] = "Gilbert";

JavaScript vs JSON Arrays

JavaScript arrays can also be used as JSON The same way JavaScript objects can be used as JSON.