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?)
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.
formik
Build forms in React, without the tears