Using jQuery, how can I find if a form has changed? [duplicate]

Question

I want to know if a form has changed at all. The form can contain any form element, such as input, select, textarea etc. Basically I want a way to display to the user that they have unsaved changed made to a form.

How can I do this using jQuery?

To clarify: I want to catch ANY change to the form, not only to input elements but to all other form elements as well, textarea, select etc.

Answer 1

The approach I usually take in such a case is that I check serialized form value. So the idea is that you calculate initial form state with $.fn.serialize method. Then when needed you just compare current state with the original serialized string.

To target all input elements (select, textarea, checkbox, input-text, etc.) within a form you can use pseudo selector :input.

For example:

var $form = $('form'),
    origForm = $form.serialize();

$('form :input').on('change input', function() {
    $('.change-message').toggle($form.serialize() !== origForm);
});

.change-message {
    display: none;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<form>
    <div class="change-message">You have unsaved changes.</div>
    <div>
        <textarea name="description" cols="30" rows="3"></textarea>
    </div>
    <div>Username: <input type="text" name="username" /></div>
     <div>
        Type: 
        <select name="type">
            <option value="1">Option 1</option>
            <option value="2" selected>Option 2</option>
            <option value="3">Option 3</option>
        </select>
    </div>
    <div>
        Status: <input type="checkbox" name="status" value="1" /> 1
        <input type="checkbox" name="status" value="2" /> 2
    </div>
</form>