How to filter in lodash when there is an unknown key

问题

I am trying to filter by child elements in lodash. I use firebase, which generates random keys for objects. The data structure here is like:

contact: {
  name: My Name,
  events: {
    -fdhu9euwf9hud: {
      eventName: day 1
      courseId: -3jfe2j09ej
    }
    -efdshkfhhiufd: {
      eventName: day 2
      courseId: -3jfe2j09ej
    }
    -fh9238fh9duf2: {
      eventName: day 1
      courseId: -dvh89wdfhoiw
    }
  }
}

I am trying to find all people (and events) that belong to a certain course which will be passed in as searchCourseID. I just don't know what to use for MYSTERYKEY below or if there is another way I should be handling this situation.

contactsWithCourse = (
    _(this.props.contacts)
        .filter(({events}) => {
             if (events && events[MYSTERYKEY].courseId == searchCourseID) {
                return true
            } else {
                return false
            }
        }
)

回答1:

You can filter the results using by iterating the events using _.some(), and check if at least one of them contains the requested searchCourseID. Note that collection methods, such as _.some() and _.filter() can work on arrays and objects (collections), and "ignore" the (mystery) keys of the items in the objects:

const result = _.filter(contacts, ({
  events
}) => _.some(events, ({
  courseId
}) => courseId === searchCourseID));

const searchCourseID = '-dvh89wdfhoiw';

const contacts = {
  '-uf39uhef2': {
    name: 'My Name',
    events: {
      '-fdhu9euwf9hud': {
        eventName: 'day 1',
        courseId: '-3jfe2j09ej'
      },
      '-efdshkfhhiufd': {
        eventName: 'day 2',
        courseId: '-3jfe2j09ej'
      },
      '-fh9238fh9duf2': {
        eventName: 'day 1',
        courseId: '-dvh89wdfhoiw'
      }
    }
  },
  '-willBeFiltered': {
    name: 'filtered out',
    events: {
      '-fdhu9euwf9hud': {
        eventName: 'day 1',
        courseId: '-3jfe123123'
      },
      '-efdshkfhhiufd': {
        eventName: 'day 2',
        courseId: '-3jfedf3433'
      },
      '-fh9238fh9duf2': {
        eventName: 'day 1',
        courseId: '-dvh8111111'
      }
    }
  }
};

const result = _.filter(contacts, ({
  events
}) => _.some(events, ({
  courseId
}) => courseId === searchCourseID));

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.2/lodash.min.js"></script>

The same logic works without lodash, using ES6 Object.values():

const result = Object.values(contacts).filter(({
  events
}) => Object.values(events).some(({
  courseId
}) => courseId === searchCourseID));

const searchCourseID = '-dvh89wdfhoiw';

const contacts = {
  '-uf39uhef2': {
    name: 'My Name',
    events: {
      '-fdhu9euwf9hud': {
        eventName: 'day 1',
        courseId: '-3jfe2j09ej'
      },
      '-efdshkfhhiufd': {
        eventName: 'day 2',
        courseId: '-3jfe2j09ej'
      },
      '-fh9238fh9duf2': {
        eventName: 'day 1',
        courseId: '-dvh89wdfhoiw'
      }
    }
  },
  '-willBeFiltered': {
    name: 'filtered out',
    events: {
      '-fdhu9euwf9hud': {
        eventName: 'day 1',
        courseId: '-3jfe123123'
      },
      '-efdshkfhhiufd': {
        eventName: 'day 2',
        courseId: '-3jfedf3433'
      },
      '-fh9238fh9duf2': {
        eventName: 'day 1',
        courseId: '-dvh8111111'
      }
    }
  }
};

const result = Object.values(contacts).filter(({
  events
}) => Object.values(events).some(({
  courseId
}) => courseId === searchCourseID));

console.log(result);

回答2:

to avoid unknown keys use _.values

_.filter(contacts, (user) => {
    return _.chain(user)
        .get('events')
        .values()
        .map('courseId')
        .includes(searchCourseID)
        .value();
});

来源：https://stackoverflow.com/questions/40824649/how-to-filter-in-lodash-when-there-is-an-unknown-key

标签

reactjs

lodash