JavaScript JSON Reference

JSON (JavaScript Object Notation)

JSON is a format for storing and transporting data.

JSON is text, and text can be transported anywhere, and read by any programming language.

JavaScript Objects can be converted into JSON, and JSON can be converted back into JavaScript Objects.

This way we can work with the data as JavaScript objects, with no complicated parsing or translations.

Example

Sending JSON:

// a JavaScript object…:
var myObj = { “name”:”John”, “age”:31, “city”:”New York” };
// …converted into JSON:
var myJSON = JSON.stringify(myObj);
// send JSON:
window.location = “demo_json.php?x=” + myJSON;

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JSON Methods

Method Description
parse() Parses a JSON string and returns a JavaScript object
stringify() Convert a JavaScript object to a JSON string

Valid Data Types

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

  • a string
  • a number
  • an object (containing valid JSON values)
  • an array
  • a boolean
  • null

JSON values cannot be one of the following data types:

  • a function
  • a date
  • undefined

More Examples

Example

Receiving JSON:

//myJSON is text received in JSON format.
//Convert JSON into a JavaScript object:
var myObj = JSON.parse(myJSON);
document.getElementById(“demo”).innerHTML = myObj.name;

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Example

Storing data as JSON, using localStorage

//Storing data:
myObj = { “name”:”John”, “age”:31, “city”:”New York” };
myJSON = JSON.stringify(myObj);
localStorage.setItem(“testJSON”, myJSON);//Retrieving data:
text = localStorage.getItem(“testJSON”);
obj = JSON.parse(text);
document.getElementById(“demo”).innerHTML = obj.name;

Try it Yourself »

Learn more about JSON in our JSON tutorial.