无法在ES6类定义中定义原型属性 [英] Cannot define prototype properties within ES6 class definition

问题描述

我正在尝试ES6语法并发现我无法在类定义中定义原型属性或实例属性，为什么禁止它？

我使用的是 MyClass.prototype.prop = 1 之前，按照下面的babel编译器尝试ES7，仍然无法定义原型属性。

  class MyClass {
 prop = 1; 
 static sProp = 1; 
} 
  

我不认为定义实例属性是危险的，有2个案例在我自己的浏览器游戏需要原型属性：

1. 子类实例需要从基类继承相同的属性值：

     var Building = function（）{...} 
    Building.prototype.sight = 350; 
    TerranBuilding.CommandCenter = ...（CommandCenter扩展建筑物）
    TerranBuilding.Barracks = ...（军营延伸建筑物）
     

因此，CommandCenter和军营将拥有与350相同的建筑物视野。

 新的CommandCenter（）。视线===新军营（）。视线//所有建筑物都有相同的视线
  

2. 缓冲区效果覆盖原始属性并删除缓冲区
   

     Marine.prototype.speed = 20 
    var unit = new Marine（）
    unit.speed === 20 //获取单位。 __proto __。速度20 
    unit.speed = 5 //缓冲区：减慢速度，unit.speed将覆盖单位.__ proto __。速度
   删除unit.speed //删除缓冲区
    unit.speed === 20 //真实，速度恢复
     

所以我认为它应该添加一种方法来设置原型属性而不是完全禁止它，或者你能提供一些其他解决方案来处理上述2种情况吗？

解决方案

这些都不会出现在类原型上。

类Foo {bar = 1; } 语法将为类实例，使用 this.bar 进行访问。

类Foo {静态条= 1; } 语法将为 Foo.bar 进行访在这种情况下，没有太多理由使用原型。它只会使实际拥有该属性的人变得复杂，并且在几个不同的类中分配一个数字将具有非常小的开销。

我建议使用类实例属性，只需在需要的地方使用 this.sight 。

I was trying ES6 syntax and find I cannot define prototype property or instance property within class defination, why forbids it?

I was using MyClass.prototype.prop=1 before, try ES7 by babel compiler as below, still cannot define prototype property.

class MyClass{
  prop=1;
  static sProp=1;
}

I don't think define instance property is any dangerous, there's 2 cases in my own browser game need prototype property:

1. Subclass instances need to inherit same property value from base class:

   var Building=function(){...}
   Building.prototype.sight=350;
   TerranBuilding.CommandCenter=...(CommandCenter extends Building)
   TerranBuilding.Barracks=...(Barracks extends Building)
   

So CommandCenter and Barracks will both have same building sight as 350.

new CommandCenter().sight===new Barracks().sight//All buildings have same sight

2. Buffer effect override original property and remove buffer
   

   Marine.prototype.speed=20
   var unit=new Marine()
   unit.speed===20//get unit.__proto__.speed 20
   unit.speed=5//Buffer:slow down speed, unit.speed will override unit.__proto__.speed
   delete unit.speed//Remove buffer
   unit.speed===20//true, speed restore
   

So I think it should add a way to set prototype property instead of forbid it completely, or can you give some other solutions to deal with above 2 cases?

解决方案

Neither of those will be on the class prototype.

The class Foo { bar = 1; } syntax will assign a value to the class instance, to be accessed with this.bar.

The class Foo { static bar = 1; } syntax will assign a value to the class constructor, to be accessed with Foo.bar.

There isn't much reason to use the prototype in this case. It will only complicate who actually owns the property and assigning a number in a few different classes will have very little overhead.

I would suggest the class instance property and just use this.sight everywhere you need it.

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