The dirtyFields plugin was born out of the need to make a user aware that they had unsaved values on an HTML form.
When applied, the dirtyFields plugin records the initial state of each form element. Any time a field is "dirtied", a CSS style is applied the text associated with the element. The form can also be styled to denote the presence of dirty fields.
It seems like a simple task at first: it's easy to use jQuery to bind an event to a text input or a <textarea> such that, when a change is made to the value, the text element is styled to look visually different (like changing the border color). But you can't do that with <select> drop-downs, checkboxes, or radio buttons.
This plugin gets around that problem by letting you apply whatever CSS class you want to use to indicate that a field has been changed to a contextually-related element, like a <label> element for the field, or an adjacent <span> or <div>, or any element you somehow associate with that form field: the plugin options give you complete control over what gets styled to indicate a field has been changed/made "dirty".
dirtyFields also gives you the option to apply a style to a container element (a <form>, a <div> containing multiple forms, whatever) that indicates that the form is dirty whenver one or more of the form field elements within the container is dirty. This option comes in handy when you want a more noticable indicator that the user needs to save the form to perserve their changes or when not all of the form fields are visible on a single screen.
The plugin works on select boxes, checkboxes, and radio buttons as well. You can control what text receives the style change.
The plugin determines if a form field is dirty by comparing the current value/state of the form field element with its previous value/state, which the plugin stores "within" the field element using jQuery's data() function. That previous value/state is set for each form field when the plugin is first executed or when the plugin's formSaved() public function is executed. dirtyFields comes with a number of public functions that let you take advantage of this feature: you can rollback individual form field values, programmatically change the value/state of any form field and still trigger the plugin routine that determines if the field has changed, or reset the entire form back to its previously saved state. There are even public functions to help you apply the plugin to form fields dynamically added to the form later via Javascript.
Finally, there are callback functions incorporated into the plugin that let you execute your own functions before or after the plugin routine that determines if a field has changed and after the plugin routine that determines if the form/form field container is dirty or not.
All of this is described in more detail on the Documentation page, and demonstrated on the Examples page.