The JSON syntax is a subset of the JavaScript syntax.
SON Syntax Rules #
JSON syntax is derived from JavaScript object notation syntax:
- Data is in name/value pairs
- Data is separated by commas
- Curly braces hold objects
- Square brackets hold arrays
"name":"John"
In JavaScript, keys can be strings, numbers, or identifier names:
JavaScript #
{ name:"John" }
JSON Values #
In JSON, values must be one of the following data types:
- a string
- a number
- an object (JSON object)
- an array
- a boolean
- null
In JavaScript values can be all of the above, plus any other valid JavaScript expression, including:
- a function
- a date
- undefined
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' }
var person = { name: "John", age: 31, city: "New York" };
You can access a JavaScript object like this:
Example #
// returns John
person.name; Data can be modified like this:
Example #
person.name = "Gilbert";
It can also be modified like this:
Example #
person["name"] = "Gilbert";
You will learn how to convert JavaScript objects into JSON later in this tutorial.
JavaScript Arrays as JSON #
The same way JavaScript objects can be used as JSON, JavaScript arrays can also be used as JSON.
You will learn more about arrays as JSON later in this tutorial.
JSON Files #
- The file type for JSON files is “.json”
- The MIME type for JSON text is “application/json”
