jquery.are-you-sure

A light-weight jQuery "dirty forms" Plugin - it monitors HTML forms and alerts users to unsaved changes if they attempt to close the browser or navigate away from the page. (Are you sure?)

angular-unsavedchanges

AngularJS directive to warn user of unsaved changes when navigating away from a form.

backform

Backform takes a Backbone model and transforms it into an HTML form. Any changes to the form are relfected back to the model and vice versa.