SITE: yourhtmlsource.com

Now we're going to get onto the dynamic parts of JavaScript. Events are occurrences triggered by a user interacting with your page, whether it be clicking on something or just moving their mouse around. By the end of this tutorial you'll have things responding to all sorts of user interactions.

One of the primary reasons JavaScript was assembled was to check whether the values entered into forms by readers were correct, thereby bypassing the lengthy trip to a CGI program to do the check. Here we'll learn the methods used to validate form input, using the onSubmit event handler.