使用默认值Array.reduce的CoffeeScript成语 [英] CoffeeScript idiom for Array.reduce with default value

问题描述

在CoffeeScript中，有时我需要调用 Array.reduce（...）使用默认值;然而，参数的不幸排序意味着初始/默认值在reduce函数本身之后，这意味着我必须使用大量的括号，这看起来比CoffeeScript要难得多。

In CoffeeScript sometimes I need to call Array.reduce(...) with a default value; however, the unfortunate ordering of the arguments means the initial/default value goes after the reduce function itself, which means I've got to use a lot of parens, which seems much uglier than CoffeeScript wants to be.

例如：

items = [ (id:'id1', name:'Foo'), (id:'id2', name:'Bar') ] # ...
itemsById = items.reduce(((memo, item) -> # <-- Too many parens!
  memo[item.id] = item
  memo), {}) # Ugly!

在CS中有更多惯用的方法吗？

Is there a more idiomatic way to do this in CS?

推荐答案

我自己和其他函数一起运行。如果它真的做了一些东西（或者它只是真的困扰我），我可能声明函数在其他地方（也许在该行之上），然后传递函数作为参数，像这样：

I've run in to this myself with other functions. In cases where its really made a mess of things (or it just really bothers me), I might declare the function elsewhere (perhaps above that line), and then pass the function as a parameter, something like so:

reduce_callback = (memo, item) ->
    memo[item.id] = item
    memo

itemsById = items.reduce reduce_callback, {}

不幸的是，你需要垂直扩展，这可能是可能的，也可能不是。这只是一个一般的建议。

Unfortunately, you expand a whole lot vertically, which may or may not be desirable. This is merely a general suggestion.

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