Chapter 18. Forms and Form Elements

As shown in examples throughout this book, HTML forms are an important component of many client-side 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.[*]

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 may respond by changing the value displayed in some other element of the form.

With server-side programs, an HTML form isn’t useful unless it has a Submit button (or unless it has only a single text input field that allows the user to press the Enter key as a shortcut for submission). ...

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