Activating OnBeforeUnload ONLY when field values have changed

Question

What I\'m trying to achieve is to Warn the user of unsaved changes if he/she tries to close a page or navigate away from it without saving first.

I\'ve managed to g

Answer 1

I had a similar requirement so came up with following jQuery script:

$(document).ready(function() {
    needToConfirm = false; 
    window.onbeforeunload = askConfirm;
});

function askConfirm() {
    if (needToConfirm) {
        // Put your custom message here 
        return "Your unsaved data will be lost."; 
    }
}

$("select,input,textarea").change(function() {
    needToConfirm = true;
});

The above code checks the needToConfirm variable, if its true then it will display warning message. Whenever input, select or textarea elements value is changed, needToConfirm variable is set to true.

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PS: Firefox > 4 don't allow custom message for onbeforeunload.
Reference: https://bugzilla.mozilla.org/show_bug.cgi?id=588292

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UPDATE: If you are a performance freak, you will love @KyleMit's suggestion. He wrote a jQuery extension only() which will be executed only once for any element.

$.fn.only = function (events, callback) {
    //The handler is executed at most once for all elements for all event types.
    var $this = $(this).on(events, myCallback);
    function myCallback(e) {
        $this.off(events, myCallback);
        callback.call(this, e);
    }
    return this
};    

$(":input").only('change', function() {
    needToConfirm = true;
});