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JSON Server

JSON is used 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 data is stored in a JavaScript object, convert the object into JSON, and send it to a server.

Example

<!DOCTYPE html>

<html>

<body>

<h2>Convert a JavaScript object into a JSON string, and send it to the server.</h2>

<script>

const myObj = { name: “John”, age: 31, city: “New York” };

const myJSON = JSON.stringify(myObj);

window.location = “demo_json.php?x=” + myJSON;

</script>

</body>

</html>

Output

demo_json.php:

John from New York is 31

Receiving Data

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

Example

<!DOCTYPE html>

<html>

<body>

<h2>Convert a JSON string into a JavaScript object.</h2>

<p id=”demo”></p>

<script>

const myJSON = ‘{“name”:”John”, “age”:31, “city”:”New York”}’;

const myObj = JSON.parse(myJSON);

document.getElementById(“demo”).innerHTML = myObj.name;

</script>

</body>

</html>

Output

Convert a JSON string into a JavaScript object.

JSON From a Server

JSON can be requested 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.

<!DOCTYPE html>

<html>

<body>

<h2>Fetch a JSON file with XMLHttpRequest</h2>

<p id=”demo”></p>

<script>

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();

</script>

</body>

</html>

Output

Fetch a JSON file with XMLHttpRequest

John

Array as JSON

While using the JSON.parse() on JSON is derived from an array, the method returns a JavaScript array, instead of a JavaScript object.

Example

<!DOCTYPE html>

<html>

<body>

<h2>Fetch a JSON file with XMLHttpRequest</h2>

<p>Content written as a JSON array will be converted into a JavaScript array.</p>

<p id=”demo”></p>

<script>

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();

</script>

</body>

</html>

Output

Fetch a JSON file with XMLHttpRequest

Content written as a JSON array will be converted into a JavaScript array.

Ford


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