分组对象数组的最有效方法 [英] Most efficient method to groupby on a array of objects

问题描述

对数组中的对象进行分组的最有效方法是什么？

What is the most efficient way to groupby objects in an array?

例如，给定此对象数组：

For example, given this array of objects:

[ 
    { Phase: "Phase 1", Step: "Step 1", Task: "Task 1", Value: "5" },
    { Phase: "Phase 1", Step: "Step 1", Task: "Task 2", Value: "10" },
    { Phase: "Phase 1", Step: "Step 2", Task: "Task 1", Value: "15" },
    { Phase: "Phase 1", Step: "Step 2", Task: "Task 2", Value: "20" },
    { Phase: "Phase 2", Step: "Step 1", Task: "Task 1", Value: "25" },
    { Phase: "Phase 2", Step: "Step 1", Task: "Task 2", Value: "30" },
    { Phase: "Phase 2", Step: "Step 2", Task: "Task 1", Value: "35" },
    { Phase: "Phase 2", Step: "Step 2", Task: "Task 2", Value: "40" }
]

我在表格中显示此信息。我想用不同的方法进行分组，但我想对这些值求和。

I’m displaying this information in a table. I’d like to groupby different methods, but I want to sum the values.

我正在使用Underscore.js作为其groupby函数，这很有帮助，但是没有不要做整个技巧，因为我不希望它们拆分但是合并，更像是组的SQL 组。

I’m using Underscore.js for its groupby function, which is helpful, but doesn’t do the whole trick, because I don’t want them "split up" but "merged", more like the SQL group by method.

我正在寻找的是能够总计特定值（如果要求）。

What I’m looking for would be able to total specific values (if requested).

所以如果我做了groupby 阶段，我想收到：

So if I did groupby Phase, I’d want to receive:

[
    { Phase: "Phase 1", Value: 50 },
    { Phase: "Phase 2", Value: 130 }
]

如果我做了分组阶段 / Step ，我会收到：

And if I did groupy Phase / Step, I’d receive:

[
    { Phase: "Phase 1", Step: "Step 1", Value: 15 },
    { Phase: "Phase 1", Step: "Step 2", Value: 35 },
    { Phase: "Phase 2", Step: "Step 1", Value: 55 },
    { Phase: "Phase 2", Step: "Step 2", Value: 75 }
]

是否有一个有用的脚本，或者我应该坚持使用Underscore.js，然后循环结果对象自己做总计？

Is there a helpful script for this, or should I stick to using Underscore.js, and then looping through the resulting object to do the totals myself?

推荐答案

如果你想避免使用外部库，你可以简洁地实现一个vanilla版本的 groupBy（），如下所示：

If you want to avoid external libraries, you can concisely implement a vanilla version of groupBy() like so:

var groupBy = function(xs, key) {
  return xs.reduce(function(rv, x) {
    (rv[x[key]] = rv[x[key]] || []).push(x);
    return rv;
  }, {});
};

console.log(groupBy(['one', 'two', 'three'], 'length'));

// => {3: ["one", "two"], 5: ["three"]}

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