第一種：function Point(x, y) {  this.x = x;  this.y = y;}Point.prototype.add= function () {  return this.x};var p = new Point(1, 2);第二種：function point2(x,y){  var o = {};  o.x = x;  o.y = y;  o.add= function(){    return o.x  }  return o}var p1 = point2(1,2)請問兩者之間的差異？