如何使用 Lodash 基于一个键合并两个集合? [英] How to use Lodash to merge two collections based on a key?

问题描述

我有两个集合，对象有一个公共键userId".如下:

I have two collections, and the objects have a common key "userId". As below:

var _= require('lodash');

var a = [
  { userId:"p1", item:1},
  { userId:"p2", item:2},
  { userId:"p3", item:4}
];

var b = [
  { userId:"p1", profile:1},
  { userId:"p2", profile:2}
];

我想根据userId"合并它们来生成:

I want to merge them based on "userId" to produce:

[ { userId: 'p1', item: 1, profile: 1 },
  { userId: 'p2', item: 2, profile:2 },
  { userId: 'p3', item: 4 } ]

到目前为止我有这些:

var u = _.uniq(_.union(a, b), false, _.property('userId'));

结果:

[ { userId: 'p1', item: 1 },
  { userId: 'p2', item: 2 },
  { userId: 'p3', item: 4 },
  { userId: 'p1', profile: 1 },
  { userId: 'p2', profile: 2 } ]

我现在如何合并它们?

我试过 _.keyBy 但结果是:

I tried _.keyBy but it results in:

{ p1: { userId: 'p1', profile: 1 },
  p2: { userId: 'p2', profile: 2 },
  p3: { userId: 'p3', item: 4 } }

这是错误的.

我应该做的最后一步是什么?

What's the last step I should do?

推荐答案

投票第二高的答案没有正确合并.如果第二个数组包含唯一属性，则不考虑.

Second highest voted answer doesn't do proper merge. If second array contains an unique property, it is not taken into account.

这种方法进行了适当的合并.

This approach does a proper merge.

var a = [
  { userId:"p1", item:1},
  { userId:"p2", item:2},
  { userId:"p3", item:4}
];

var b = [
  { userId:"p1", profile:1},
  { userId:"p2", profile:2},
  { userId:"p4", profile:4}
];
var merged = _.merge(_.keyBy(a, 'userId'), _.keyBy(b, 'userId'));
var values = _.values(merged);
console.log(values);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.10/lodash.min.js"></script>

// from https://stackoverflow.com/a/34749873/80766
const mergeDeep = (target, ...sources) => {
  if (!sources.length) return target;
  const source = sources.shift();

  if (target instanceof Object && source instanceof Object) {
    for (const key in source) {
      if (source[key] instanceof Object) {
        if (!target[key]) Object.assign(target, { [key]: {} });
        mergeDeep(target[key], source[key]);
      } else {
        Object.assign(target, { [key]: source[key] });
      }
    }
  }

  return mergeDeep(target, ...sources);
}

const a = [
  { userId:"p1", item:1},
  { userId:"p2", item:2},
  { userId:"p3", item:4}
];

const b = [
  { userId:"p1", profile:1},
  { userId:"p2", profile:2},
  { userId:"p4", profile:4}
];


const aKeyed = a.reduce((acc, cur) => ({ ...acc, [cur.userId]: cur }), {});
const bKeyed = b.reduce((acc, cur) => ({ ...acc, [cur.userId]: cur }), {});
const merged = mergeDeep(aKeyed, bKeyed);
const values = Object.values(merged);
console.log(values);

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