HTML forms are an important part of interacting with the user. Typically, the user enters data into the form, and it is then sent to the web server for further processing.
JavaScript can also process form data within the browser. Sometimes, this is to allow it to preprocess or check the data before it is sent to the server, but sometimes it all stays within the browser and doesn’t need to be sent off.
Traditionally, JavaScript has been used for data validation: checking whether the form has been filled in properly ...
