ASP.NET/Webform Textbox does not fire the autopostback when onkeyup event defines "setTimeout" (IE9)

Question

I've a strange situation on IE 9. It just works in Chrome and Firefox. I will post only the relevant code.

It's a legacy application (VS2008). The "corp framework" defines field masks at runtime, it uses the onkeyup event, with javascript like this:

Javascript:

function mascara(o, f) {
    v_obj = o
    v_fun = f

    setTimeout(function() {
    v_obj.value = v_fun(v_obj.value)
    }, 1)
}

ASP.NET HTML:

<asp:TextBox runat="server" ID="TextBox5" AutoPostBack="true" OnTextChanged="TextChanged" />

The mask and the postback event works in all browsers except IE9. When I remove the setTimeout in the javascript mask function, the postback works, but i lost the mask behavior.

I figure out that AutoPostBack=true will render the onchange event with setTimeout. The mask uses another time the setTimeout function, when I remove the setTimeout in the mask, the postback works at IE 9.

Rendered HTML:

<input name="TextBox5" type="text" onchange="javascript:setTimeout('__doPostBack(\'MPTextBox5\',\'\')', 0)" onkeypress="if (WebForm_TextBoxKeyHandler(event) == false) return false;" id="MPTextBox5" onkeyup="mascara(this, mnum);">

I can't figure out what is the problem at IE9 and the solution.

Answer 1

MS will not fix this bug:

https://connect.microsoft.com/IE/feedback/details/761843/wont-fire-change-event-if-value-of-input-is-changed-using-keyup

Workaround found at: http://bugs.jquery.com/ticket/10818

// Set value for IE without clearing the "changed" flag
this.innerText = val;
// Set value for everyone else
if ( this.value != val ) {
   this.value = val;
}