jQuery UI Dialog Buttons from variables

I have variables holding the translated labels for buttons inside a jquery ui dialog.

I cannot fill the button array key with the variable itself, and can't find any way to let it treat my variable just as string.

translations['ok'] = 'ok';
translatinos['cancel'] = 'cancel';

// not working
jQuery('#foo').dialog({
    buttons:
    {
        translations['ok']: function() { alert('foo-ok'); },
        translations['cancel']: function() { alert('foo-cancel'); }
    }
});

// working
jQuery('#bar').dialog({
    buttons:
    {
        "Ok": function() { alert('bar-ok'); },
        "Cancel": function() { alert('bar-cancel'); }
    }
});

Is there any way to get this to work with variable array keys?