Question

给出一个包含子集合的集合（以下代码段中的users），以及另一个包含我需要合并的属性的集合（organizations），这些集合需要合并到users的子集合中，最有效的方法是什么？

下面的代码可以工作，但是嵌套迭代对我来说从来没有那么好过。此外，生产环境具有成百上千的结果，因此性能至少是一个考虑因素。

仅供参考，我正在利用lodash库，并且知道使用该库 not 会带来一些性能提升-但是，我希望有人可以提供更多的性能解决问题的有效方法。

下面的代码查找组织的名称，然后将该名称添加到users数组中以供应用程序的其他部分使用。

（数据结构来自API，无法更改。）

// organizations are actually fetched from an API via Observable.  Can change at any time.
const organizations = [{
    organization_id: 5,
    organization_name: 'Sample 1'
  },
  {
    organization_id: 6,
    organization_name: 'Sample 2'
  },
  {
    organization_id: 9,
    organization_name: 'Sample 3'
  },
  // etc...
];

// users are actually fetched from an API via Observable.  Can change at any time.
const users = [{
    user_name: 'User 1',
    organizations: [{
        organization_id: 9,
        organization_role: 'Limited'
      },
      {
        organization_id: 6,
        organization_role: 'Admin'
      }
    ]
  },
  {
    user_name: 'User 2',
    organizations: [{
        organization_id: 5,
        organization_role: 'Limited'
      },
      {
        organization_id: 6,
        organization_role: 'Limited'
      }
    ]
  },
  // etc...
];


document.addEventListener('DOMContentLoaded', () => {
  _.forEach(users, (user) => {
    _.forEach(user.organizations, (organization) => {
      organization.organization_name = _.get(_.find(organizations, ['organization_id', organization.organization_id]), 'organization_name', '?');
    });
  });
  console.log(users);
}, false);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.min.js"></script>

Answer 1

由于_.find()是一个O（n）操作（其中n是组织const的长度），而forEach操作是O（m * l）（m个用户，l个平均每个组织的数目用户），则总操作为O（n * m * l）。您可以通过首先映射组织将其降低为O（n + m * l），这是一个O（n）操作（例如，使用_.keyBy()）。

// organizations are actually fetched from an API via Observable.  Can change at any time.
const organizations = [{"organization_id":5,"organization_name":"Sample 1"},{"organization_id":6,"organization_name":"Sample 2"},{"organization_id":9,"organization_name":"Sample 3"}];

// users are actually fetched from an API via Observable.  Can change at any time.
const users = [{"user_name":"User 1","organizations":[{"organization_id":9,"organization_role":"Limited"},{"organization_id":6,"organization_role":"Admin"}]},{"user_name":"User 2","organizations":[{"organization_id":5,"organization_role":"Limited"},{"organization_id":6,"organization_role":"Limited"}]}];


document.addEventListener('DOMContentLoaded', () => {
  const orgDict = _.keyBy(organizations, 'organization_id');
  _.forEach(users, (user) => {
    _.forEach(user.organizations, (organization) => {
      organization.organization_name = _.get(orgDict['organization_id'], 'organization_name', '?');
    });
  });
  console.log(users);
}, false);

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将一个数组中的值分配给嵌套数组的最有效方法

1 个答案: