使用元组或对象进行映射 [英] Map using tuples or objects

问题描述

我正在尝试使用新的(ES6) Map 对象，以表示属性和值之间的映射.

I'm trying to use the new (ES6) Map objects in order to represent a map between properties and a value.

我的对象的形式类似于:

I have objects in a form similar to:

 {key1:value1_1,key2:value2_1},..... {key1:value1_N,key2:value2_N}

我想根据两者的key1 和 key2值对它们进行分组.

I want to group them based on both their key1 and key2 value.

例如，我希望能够按x和y将以下内容分组:

For example, I want to be able to group the following by x and y:

[{x:3,y:5,z:3},{x:3,y:4,z:4},{x:3,y:4,z:7},{x:3,y:1,z:1},{x:3,y:5,z:4}]

并获取包含以下内容的地图:

And obtain a Map containing:

{x:3,y:5} ==>  {x:3,y:5,z:3},{x:3,y:5,z:4}
{x:3,y:4} ==>  {x:3,y:4,z:4},{x:3,y:4,z:7}
{x:3,y:1} ==>  {x:3,y:1,z:1}

在Python中，我将使用元组作为字典键. ES6映射允许将任意对象用作键，但是使用标准的相等算法(===)，因此根据我的判断，对象仅按引用相等.

In Python, I'd use tuples as dictionary keys. ES6 map allow arbitrary objects as keys but use the standard equality algorithm (===) so objects are only equal by reference from what I can tell.

如何使用ES6映射完成这种分组?另外，如果我忽略了一种优雅的方法，那么可以使用普通的JS对象作为解决方案.

How can I accomplish this sort of grouping using ES6 maps? Alternatively, a solution using normal JS objects if there is an elegant way I overlooked.

我宁愿不使用外部馆藏库-但如果有一个更好的解决方案，我也有兴趣对其进行研究.

I'd rather not use an external collections library - but if there is a better solution using one I'm interested in learning about it too.

推荐答案

好，我在讨论现在，我从Mozilla的 Jason Orendorff 得到了答案:

Ok, I've raised the issue on esdiscuss now and I got an answer from Mozilla's Jason Orendorff:

1. 这 是ES6地图的问题.
2. 该解决方案将以ES7 值对象的形式出现，而不是对象
3. 之前曾考虑过让人们指定.equals和.hashCode，但是由于支持值对象而被拒绝. (我认为是有充分理由的.)
4. 到目前为止，唯一的解决方案是滚动自己的收藏集.

1. This is a problem with ES6 maps.
2. The solution will come in the form of ES7 value objects for keys instead of objects.
3. It was considered before to let people specify .equals and .hashCode but it was rejected in favor of value objects. (for good reasons in my opinion).
4. The only solution as of now is to roll your own collection.

Bradley在ESDiscuss线程上提供了一个基本的此类集合(概念，请勿在生产代码中使用)，并且可能看起来像这样:

A basic such collection (concept, don't use in production code) was offered by Bradley on the ESDiscuss thread and might look something like this:

function HashMap(hash) {
  var map = new Map;
  var _set = map.set;
  var _get = map.get;
  var _has = map.has;
  var _delete = map.delete;
  map.set = function (k,v) {
    return _set.call(map, hash(k), v);
  }
  map.get = function (k) {
    return _get.call(map, hash(k));
  }
  map.has = function (k) {
    return _has.call(map, hash(k));
  }
  map.delete = function (k) {
    return _delete.call(map, hash(k));
  }
  return map;
}

function TupleMap() {
  return new HashMap(function (tuple) {
    var keys = Object.keys(tuple).sort();
    return keys.map(function (tupleKey) { // hash based on JSON stringification
               return JSON.stringify(tupleKey) + JSON.stringify(tuple[tupleKey]);
    }).join('\n');
    return hashed;
  });
}

一个更好的解决方案是使用 MontageJS/Collections 之类的东西，它允许指定哈希/等于函数.

A better solution is to use something like MontageJS/Collections which allows for specification of hash/equals functions.

您可以在此处上查看API文档.

You can see the API docs here.

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