javascript - 对对象数组进行分组的最有效方法(Most efficient method to groupby on an array of objects)

Question

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

(在数组中对对象进行分组的最有效方法是什么？)

For example, given this array of objects:

(例如，给定此对象数组：)

[ 
    { 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" }
]

I'm displaying this information in a table.

(我正在表中显示此信息。)

I'd like to groupby different methods, but I want to sum the values.

(我想对不同的方法进行分组，但是我想对这些值求和。)

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.

(我将Underscore.js用于其groupby函数，这很有用，但并不能解决所有问题，因为我不希望它们“分裂”而是“合并”，更像SQL group by方法。)

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

(我正在寻找的是能够总计特定值（如果需要）。)

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

(因此，如果我按Phase进行groupby，则希望收到：)

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

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

(如果我对Phase / Step进行了分组，则会收到：)

[
    { 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 }
]

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?

(是否为此提供有用的脚本，还是应该坚持使用Underscore.js，然后循环遍历生成的对象来自己进行总计？)

  ask by Rail24 translate from so

Answer 1

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

(如果要避免使用外部库，则可以像这样groupBy()地实现groupBy()的groupBy()版本：)

 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"]}