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copied!<p>One piece of the puzzle:</p> <pre><code>/** * Determines if a form is dirty by comparing the current value of each element * with its default value. * * @param {Form} form the form to be checked. * @return {Boolean} <code>true</code> if the form is dirty, <code>false</code> * otherwise. */ function formIsDirty(form) { for (var i = 0; i < form.elements.length; i++) { var element = form.elements[i]; var type = element.type; if (type == "checkbox" || type == "radio") { if (element.checked != element.defaultChecked) { return true; } } else if (type == "hidden" || type == "password" || type == "text" || type == "textarea") { if (element.value != element.defaultValue) { return true; } } else if (type == "select-one" || type == "select-multiple") { for (var j = 0; j < element.options.length; j++) { if (element.options[j].selected != element.options[j].defaultSelected) { return true; } } } } return false; } </code></pre> <p><a href="http://developer.mozilla.org/en/DOM/window.onbeforeunload" rel="noreferrer">And another</a>:</p> <pre><code>window.onbeforeunload = function(e) { e = e || window.event; if (formIsDirty(document.forms["someFormOfInterest"])) { // For IE and Firefox if (e) { e.returnValue = "You have unsaved changes."; } // For Safari return "You have unsaved changes."; } }; </code></pre> <p>Wrap it all up, and what do you get?</p> <pre><code>var confirmExitIfModified = (function() { function formIsDirty(form) { // ...as above } return function(form, message) { window.onbeforeunload = function(e) { e = e || window.event; if (formIsDirty(document.forms[form])) { // For IE and Firefox if (e) { e.returnValue = message; } // For Safari return message; } }; }; })(); confirmExitIfModified("someForm", "You have unsaved changes."); </code></pre> <p>You'll probably also want to change the registration of the <code>beforeunload</code> event handler to use <code>LIBRARY_OF_CHOICE</code>'s event registration.</p>

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