根据数组中的 ID 和日期获取最新版本

Question

我有一个包含以下属性的 javascript 对象数组：_id, isVersionFrom, createdAt _id, isVersionFrom 存储了一个 mongoDb _id（当它是原始对象时，isVersionFrom 为 false）。 createdAt 有一个时代的时间戳。 现在我想为每个 _id 获取一个最新版本的数组。

例如，如果我有这个数组：

[ { _id: 'CXsqvJ3ArwpM7aQwg', createdAt: 1493630867411, isVersionFrom: false }, { _id: 'nnFthaqJ254BQozSp', createdAt: 1493630967411, isVersionFrom: 'CXsqvJ3ArwpM7aQwg' }, { _id: 'Jksfe6Aaof9hT8CW9', createdAt: 1493631067411, isVersionFrom: 'CXsqvJ3ArwpM7aQwg' }, { _id: 'HSitgQdFwYHqCjRax', createdAt: 1493631067411, isVersionFrom: false }, { _id: 'vhZZCKhyQgkNSGjqK', createdAt: 1493631077411, isVersionFrom: 'HSitgQdFwYHqCjRax' }, ]

我想要这个结果：

[ { _id: 'Jksfe6Aaof9hT8CW9', createdAt: 1493631067411, isVersionFrom: 'CXsqvJ3ArwpM7aQwg' }, { _id: 'vhZZCKhyQgkNSGjqK', createdAt: 1493631077411, isVersionFrom: 'HSitgQdFwYHqCjRax' }, ]

所以它基本上必须过滤掉所有旧版本的 id。

Answer 1

更新使用下划线的可能解决方案：

const myArray = [
  {
    _id: "CXsqvJ3ArwpM7aQwg",
    createdAt: 1493630867411,
    isVersionFrom: false
  },
  {
    _id: "nnFthaqJ254BQozSp",
    createdAt: 1493630967411,
    isVersionFrom: "CXsqvJ3ArwpM7aQwg"
  },
  {
    _id: "Jksfe6Aaof9hT8CW9",
    createdAt: 1493631067411,
    isVersionFrom: "CXsqvJ3ArwpM7aQwg"
  },
  {
    _id: "HSitgQdFwYHqCjRax",
    createdAt: 1493631067411,
    isVersionFrom: false
  },
  {
    _id: "vhZZCKhyQgkNSGjqK",
    createdAt: 1493631077411,
    isVersionFrom: "HSitgQdFwYHqCjRax"
  }
];

// Chain underscore methods to use seamlessly.
const result = _.chain(myArray)
  // Group items either by isVersionFrom or by original _id.
  .groupBy(item => (!item.isVersionFrom ? item._id : item.isVersionFrom))
  // For each group take item with max date (latest) .
  .map(val => _.max(val, item => item.createdAt))
  // Get value of chain.
  .value();