In early versions of browsers, forms were generally the only means by which a web application could interact with the user. The user could input data into a variety of form controls and send that data to the server, and a server-side application would return a web page that incorporated the data in some way. In many cases a server-side application would have to validate every field in a form, and notify the user of any errors when responding to a form submission. This experience could be frustrating for the user, as sometimes one or more fields would be cleared of any data the user had entered.
A form in an HTML page is denoted by the
<form/> element, and a single web page can have any number of forms. Quite naturally, the
document object has a
forms property — a collection of all
<form/> elements found in the document. Like all array-like objects,
document.forms has a
length property, and you can access each form by specifying the index at which a form exists within the document, ...