Point Obect

function Stack ()
{
    this.Items = null;

    this.push = function (item) {
        item.NextItem = this.Items;
        this.Items = item
    }
    this.pop = function () {
        if (this.Items == null)
            return null;
        var  item = this.Items;
        this.Items = item.NextItem;
        item.NextItem = undefined;
        return item;
    }
    this.toString = function () {
        var  s = new String("STACK DUMP:\n");
        var  item = this.Items;
        while (item) {
            s += ("{" + item.toString() + "}\n");
            item = item.NextItem; }
        return s;
    }
}