Question

;
"use strict";
function IPoint() {

  this.getDistance = function(point) {
    var x = this.x - point.x;
    var y = this.y - point.y;
    return Math.sqrt(x * x + y * y);
  };

  this.isAbove = function(point) {
    if (this.y <= point.y) {
      return true;
    } else {
      return false;
    }
  };
  this.isBelow = function(point) {
    if (this.y >= point.y) {
      return true;
    } else {
      return false;
    }
  };
  this.isLeftOf = function(point) {
    if (this.x <= point.x) {
      return true;
    } else {
      return false;
    }
  };
  this.isRightOf = function(point) {
    if (this.x >= point.x) {
      return true;
    } else {
      return false;
    }
  };
};

var Point = function(x, y) {
  this.x = x;
  this.y = y;
  IPoint.call(this);
};
Point.prototype =
  Object.create(null,
                {
                  get x() {
                    return this._x;
                  },
                  set x(v) {
                    this._x = v;
                  },
                  get y() {
                    return this._y;
                  },
                  set y(v) {
                    this._y = v;
                  },
                });

给我错误 Uncaught TypeError：属性描述必须是一个对象：undefined geometry.js：47（匿名函数）。这让我觉得我不能在dot.create中传递的对象中使用setter和getter，但我不知道为什么。我做错了什么？

Answer 1

Object.create确实将property descriptors的对象作为其第二个参数，就像defineProperties一样。正确的语法是

Point.prototype = Object.create(null, {
    x: {
        get: function() { return this._x; },
        set: function(v) { this._x = v; },
        // configurable: true,
        // enumerable: true
    },
    x: {
        get: function() { return this._y; },
        set: function(v) { this._y = v; },
        // configurable: true,
        // enumerable: true
    }
});

但是，我没有看到Point s不应该从Object继承的原因，所以就这样做吧

Point.prototype = {
    get x() { return this._x; },
    set x(v) { this._x = v; },
    get y() { return this._y; },
    set y(v) { this._y = v; }
};

我可以将mixin模式与setter和getter一起使用

1 个答案: