Forms are an essential part of HTML pages, and developers typically use JavaScript to elaborate on how they function. You can best understand the benefits of using JavaScript with HTML forms by first studying how forms work with straight HTML. The essence of a form is to accept input from the user and then submit it to a server of some kind. The server may be the back end that generated the HTML, but not necessarily.
The lifecycle of a simple HTML form is to allow the user to input data into its fields, then submit the data and reload the page. JavaScript lets us create a smoother alternative to this clunky flow of events. We can take the information from the form and submit it quietly in different ways; for example, we might update the data incrementally as the user updates the form.
