这段话怎么理解，又是new又是prototype，搞懵 了，为啥这么写呢？

Question

 var DragOp = function() {};

  DragOp.prototype = {

    start: function(){},

    drag: function(){},

    end: function(){},

    isSameItem: function() {

      return false;

    }

  };

  var SlideDrag = function(opts) {

    this.dragThresholdX = opts.dragThresholdX || 10;

    this.el = opts.el;

    this.item = opts.item;

    this.canSwipe = opts.canSwipe;

  };

  SlideDrag.prototype = new DragOp();

Answer 1

var DragOp = function() {};以函数表达式的形式创建DragOp函数DragOp.prototype ={……} 编写DragO函数的原型对象new DragOp();创建一个DragOp函数的实例SlideDrag.prototype = new DragOp();将DragOp函数的实例赋值给SlideDrag函数的原型对象，从而使得SlideDrag函数继承DragOp函数的全部属性及方法