HTML forms are a crucial component of interactive websites, enabling users to provide data that can be dispatched to a server for further processing. This data is typically structured as form data, consisting of a series of key-value pairs, where the keys correspond to the names of the form fields, and the values represent the user's input.

In JavaScript, this form data is managed using the FormData interface, a part of the Web API. The FormData object allows you to compile a set of key-value pairs, which can be dispatched using an XMLHttpRequest. Although its primary application is for transmitting form data, the FormData object can be utilized independently from forms to transfer keyed data.

Here's an extended example demonstrating how the FormData object is used in JavaScript:

let formData = new FormData();

// Append new data to the form
formData.append('username', 'JohnDoe');
formData.append('email', 'john.doe@example.com');

console.log(formData.get('username')); // JohnDoe

// Delete a value from the form data
formData.delete('username');

console.log(formData.get('username')); // null

let request = new XMLHttpRequest();
request.open('POST', 'submitform.php');
request.send(formData);

In this example, a new FormData object is instantiated, and two key-value pairs are added to it using the append() method. The get() method is then used to retrieve the value of the 'username' field, and the delete() method is used to remove the 'username' field from the form data. Finally, an XMLHttpRequest is created and opened with the "POST" method and the URL of the server-side script that will handle the form data. The form data is then dispatched to the server using the send() method of the XMLHttpRequest.