Block form submission when click back

Question

It may seem like a stupid question but I’m amazed that when I click the back button, the form is sent.

The code is similar to this:

<form id="idform" method="post" onsubmit="return funcaodevalidacao(this);">
    <!-- conteúdo do form -->
    <input type="submit" value="Enviar"> <button onclick="window.location.href = 'URL'">Voltar</button>
</form>
<script>
    $('form').submit(function (ev) {
        ev.preventDefault();
        $(window).unbind('beforeunload');
        return false;
    });
</script>

What happens is the following: when I click on Back, which should redirect me to a desired URL, the form is SENT, and then is redirected to the URL, what I don’t understand is why the form is being sent.

I tried the way described above to use preventDefault, disable beforeunload, return false, but the form is still sent.

How do I block this behavior? I’m testing in firefox.

PS: the function: function Devaluation(this) is returning false for test questions. The palliative solution I found was to remove the 'form' element, but I believe this is not the correct alternative. I checked the link http://www.w3.org/TR/html401/interact/forms.html#h-17.12 that disabling the element is also not possible.

Answer 1

In fact the form I was using in the above example adds a second call to Submit where it actually prevents form submission but still calls the validation function.

The most correct solution I thought about in this case was to add this script to the back button:

$('form').attr('onsubmit','return false;');window.location.href='URL'

This overrides the validation function that gave the impression that the form was being sent.