How can I disable a button on a jQuery UI dialog?

Looks like anyone, even in this linked question, have proposed this solution, similar to the first part of the answer given by Nick Craver:

$("#dialog").dialog({
    width: 480,
    height: "auto",
    buttons: [
        {
            id: "button-cancel",
            text: "Cancel",
            click: function() {
                $(this).dialog("close");
            }
        },
        {
            id: "button-ok",
            text: "Ok",
            click: function() {
                $(this).dialog("close");
            }
        }
    ]
});

Then, elsewhere, you should be able to use the API for the jquery UI button:

$("#button-ok").button("disable");

If you're including the .button() plugin/widget that jQuery UI contains (if you have the full library and are on 1.8+, you have it), you can use it to disable the button and update the state visually, like this:

$(".ui-dialog-buttonpane button:contains('Confirm')").button("disable");

You can give it a try here...or if you're on an older version or not using the button widget, you can disable it like this:

$(".ui-dialog-buttonpane button:contains('Confirm')").attr("disabled", true)
                                              .addClass("ui-state-disabled");

If you want it inside a specific dialog, say by ID, then do this:

$("#dialogID").next(".ui-dialog-buttonpane button:contains('Confirm')")
              .attr("disabled", true);

In other cases where :contains() might give false positives then you can use .filter() like this, but it's overkill here since you know your two buttons. If that is the case in other situations, it'd look like this:

$("#dialogID").next(".ui-dialog-buttonpane button").filter(function() {
  return $(this).text() == "Confirm";
}).attr("disabled", true);

This would prevent :contains() from matching a substring of something else.

You can also use the not now documented disabled attribute:

$("#element").dialog({
    buttons: [
    {
        text: "Confirm",
        disabled: true,
        id: "my-button-1"
    }, 
    {
        text: "Cancel",
        id: "my-button-2",
        click: function(){            
               $(this).dialog("close");
        }  

    }]
});

To enable after dialog has opened, use:

$("#my-button-1").attr('disabled', false);

JsFiddle: http://jsfiddle.net/xvt96e1p/4/

The following works from within the buttons click function:

$(function() {
    $("#dialog").dialog({
        height: 'auto', width: 700, modal: true,
        buttons: {
            'Add to request list': function(evt) {

                // get DOM element for button
                var buttonDomElement = evt.target;
                // Disable the button
                $(buttonDomElement).attr('disabled', true);

                $('form').submit();
            },
            'Cancel': function() {
                $(this).dialog('close');
            }
        }
    });
}