对对象数组进行分组的最有效方法 [英] Most efficient method to groupby on an 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?

例如，给定这个对象数组:

<预><代码>[{ 阶段:阶段 1"，步骤:步骤 1"，任务:任务 1"，值:5" },{ 阶段:阶段 1"，步骤:步骤 1"，任务:任务 2"，值:10" },{ 阶段:阶段 1"，步骤:步骤 2"，任务:任务 1"，值:15" },{ 阶段:阶段 1"，步骤:步骤 2"，任务:任务 2"，值:20" },{ 阶段:阶段 2"，步骤:步骤 1"，任务:任务 1"，值:25" },{ 阶段:阶段 2"，步骤:步骤 1"，任务:任务 2"，值:30" },{ 阶段:第 2 阶段"，步骤:第 2 步"，任务:任务 1"，值:35"}，{ 阶段:阶段 2"，步骤:步骤 2"，任务:任务 2"，值:40"}]

我将这些信息显示在表格中.我想按不同的方法分组，但我想对值求和.

我将 Underscore.js 用于它的 groupby 函数，这很有帮助，但并没有完成整个技巧，因为我不希望它们拆分"而是合并"，更像是 SQL group by 方法.

我正在寻找的是能够总计特定值(如果需要).

因此，如果我按 Phase 进行分组，我希望收到:

<预><代码>[{ 阶段:阶段 1"，值:50 }，{ 阶段:阶段 2"，值:130 }]

如果我做了 groupy Phase/Step，我会收到:

<预><代码>[{ 阶段:第 1 阶段"，步骤:第 1 步"，值:15 }，{ 阶段:阶段 1"，步骤:步骤 2"，值:35 }，{ 阶段:第 2 阶段"，步骤:第 1 步"，值:55 }，{ 阶段:阶段 2"，步骤:步骤 2"，值:75 }]

是否有一个有用的脚本，或者我应该坚持使用 Underscore.js，然后循环遍历结果对象以自己计算总数?

解决方案

如果你想避免使用外部库，你可以像这样简洁地实现一个普通版本的 groupBy():

var groupBy = function(xs, key) {返回 xs.reduce(function(rv, x) {(rv[x[key]] = rv[x[key]] || []).push(x);返回房车；}, {});};console.log(groupBy(['one', 'two', 'three'], 'length'));//=>{3: ["一", "二"], 5: ["三"]}

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

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" }
]

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

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.

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

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

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

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 }
]

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?

解决方案

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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