Question

我有以下coffeescript类

class Data
  constructor: (data)->
    data.prototype.meta = @meta
    return data
  meta: ->
    return { id: 123 }

# this is how I want to work with it, as an example
a = {name: "val"}
x = new Data a

for key, item of x
   console.log key, item ## should say `name`, `val` (not meta)

console.log x.meta ## should say `{id:123}

我想将meta属性添加到现有object，但是当我循环播放时， NOT 希望meta出现使用for循环的新对象x。

如果我没有正确解释这个问题，请告诉我，我会尽力做得更好：）

Answer 1

您可以使用Object.defineProperty()：

class Data
  constructor: (data) ->
    Object.defineProperty(data, "meta", { enumerable: false, value: @meta });
    return data
  meta: { id: 123 }

a = {name: "val"}
x = new Data(a)

for key, item of x
   console.log key, item ## should say `name`, `val` (not meta)

console.log x.meta ## should say `{id:123}

Answer 2

A最终使用以下内容......

a = {name: "val"}
a.meta = {id: 123} ## as normal
Object.defineProperty a, "meta", enumerable: false ## this hides it from loops


for key, item of x
   console.log key, item ## should say `name`, `val` (not meta)

console.log x.meta ## should say `{id:123}

扩展具有隐藏属性的对象

2 个答案: