JavaScript: The Definitive Guide, Fourth Edition

Chapter 15. Forms and Form Elements

As we’ve seen in examples throughout this book, the use of HTML forms is basic to almost all JavaScript programs. This chapter explains the details of programming with forms in JavaScript. It is assumed that you are already somewhat familiar with the creation of HTML forms and with the input elements that they contain. If not, you may want to refer to a good book on HTML.^[50] The client-side reference section of this book lists the HTML syntax along with the JavaScript syntax for forms and form elements; you may find these useful for quick reference.

If you are already familiar with server-side programming using HTML forms, you may find that things are done differently when forms are used with JavaScript. In the server-side model, a form with the input data it contains is submitted to the web server all at once. The emphasis is on processing a complete batch of input data and dynamically producing a new web page in response. With JavaScript, the programming model is quite different. In JavaScript programs, the emphasis is not on form submission and processing but instead on event handling. A form and all input elements in it have event handlers that JavaScript can use to respond to user interactions within the form. If the user clicks on a checkbox, for example, a JavaScript program can receive notification through an event handler and might respond by changing the value displayed in some other element of the form.

With server-side programs, ...