function PlaceHolder(id) {
    self = this;

    item = document.getElementById(id);

    item.onclick = function () {
        self.limpar(item);
    }

    item.onfocus = function () {
        self.limpar(item);
    }

    self.limpar = function (item) {
        lastValue = item.value;
        item.value = '';
    }
}

var txt = new PlaceHolder('endCliente');