Window on before unload - for stop user to escape page before all data is not saved or an action not performed

on_before_unload.js

// Message to be displayed on unload
var message = $('#jtrnslt #leavemess').text(), submitting = false;
// On Form submition set submitting to true for not fire onbeforeunload
$(document).on("submit", "form", function(event){
	submitting = true;
});
// Window onbeforeunload fired when leave page but not if it a form submition or element with .noBeforeUnload class
window.onbeforeunload = function (e) {
	e = e || window.event;
	// Determine if you want to allow unload
	/* some synchronous operation here*/
	if (!submitting && !$(e.target.activeElement).hasClass('noBeforeUnload')) {
		// IE BUG: throws unspecified error on "cancel"
		// so we temporarily mask all Javascript errors
		window.onerror = function (msg, url, linenumber) {
			return -1 < msg.toLowerCase().indexOf('unspecified error');
		};
		// After return the (blocking) confirmation window is shown
		// after which we remove Javascript error handler
		window.setTimeout(function () { 
			window.onerror = function () {
				return false;
			}
		}, 100);
		// -- IE BUG
		// IE expects the confirmation string in the 
		// `returnValue` property of event object
		if (e) {
			e.returnValue = message;
		}
		// Other browsers expect it returned as a string
		return message;
	}
};

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