The JSON syntax is a simplified version of the JavaScript syntax.
JSON syntax is based on JavaScript object notation:
JSON data is composed of name/value pairs (also known as key/value pairs).
Each pair consists of a field name (in double quotes), followed by a colon, and then the corresponding value.
| “name”:“John” |
| In JSON, names (or keys) must be enclosed in double quotes. |
The JSON format closely resembles JavaScript objects, but in JSON, keys must be strings enclosed in double quotes.
| {“name”:“John”} |
In JavaScript, keys can be strings, numbers, or identifier names.
| {name:“John”} |
In JSON, values must be one of the following data types:
In JavaScript, values can be all of the above, plus other valid expressions such as:
Additionally, in JSON, string values must always be enclosed in double quotes.
| {“name”:“John”} |
In JavaScript, string values can be written using either double or single quotes.
| {name:‘John’} |
Since JSON syntax is based on JavaScript object notation, minimal additional software is required to work with JSON in JavaScript.
In JavaScript, you can create an object and assign data to it like this:
| person = {name:“John”, age:31, city:“New York”}; |
You can access a JavaScript object like this:
| // returns John person.name; |
It can also be accessed in this manner:
| // returns John person[“name”]; |
Data can be updated in the following way:
| person.name = “Gilbert”; |
Later in this tutorial, you will learn how to convert JavaScript objects into JSON.
Just like JavaScript objects, JavaScript arrays can also be written as JSON. You will learn more about objects and arrays later in this tutorial.
JSON files have the “.json” extension, and the MIME type for JSON text is “application/json”.