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A common use of JSON is to exchange data to/from a web server.

When receiving data from a web server, the data is always a string.

Parse the data with JSON.parse(), and the data becomes a JavaScript object.

Sending Data

If you have data stored in a JavaScript object, you can convert the object into JSON, and send it to a server:

Example

const myObj = {name: "John", age: 31, city: "New York"};
const myJSON = JSON.stringify(myObj);
window.location = "demo_json.php?x=" + myJSON;

Receiving Data

If you receive data in JSON format, you can easily convert it into a JavaScript object:

Example

const myJSON = '{"name":"John", "age":31, "city":"New York"}';
const myObj = JSON.parse(myJSON);
document.getElementById("demo").innerHTML = myObj.name;

JSON From a Server

You can request JSON from the server by using an AJAX request

As long as the response from the server is written in JSON format, you can parse the string into a JavaScript object.

Example

Use the XMLHttpRequest to get data from the server:

const xmlhttp = new XMLHttpRequest();
xmlhttp.onload = function() {
  const myObj = JSON.parse(this.responseText);
  document.getElementById("demo").innerHTML = myObj.name;
};
xmlhttp.open("GET", "json_demo.txt");
xmlhttp.send();

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Array as JSON

When using the JSON.parse() on JSON derived from an array, the method will return a JavaScript array, instead of a JavaScript object.

Example

JSON returned from a server as an array:

const xmlhttp = new XMLHttpRequest();
xmlhttp.onload = function() {
  const myArr = JSON.parse(this.responseText);
  document.getElementById("demo").innerHTML = myArr[0];
  }
}
xmlhttp.open("GET", "json_demo_array.txt", true);
xmlhttp.send();

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