Lodash union of arrays of objects

问题

I'd like to use the _.union function to create a union of two arrays of objects. Union works with arrays of primitives only as it uses === to examine if two values are equal.

I'd like to compare objects using a key property: objects with the same key property would be regarded equal. Is there a nice functional way to achieve that ideally using lodash?

回答1:

A non pure lodash way to do this but using the array.concat function you are able to do this pretty simply along uniq():

var objUnion = function(array1, array2, matcher) {
  var concated = array1.concat(array2)
  return _.uniq(concated, false, matcher);
}

An alternative approach would be to use flatten() and uniq():

var union = _.uniq(_.flatten([array1, array2]), matcherFn);

回答2:

And what about UniqBy with a concat of the two arrays before?

_.uniqBy([{ 'x': 1 }, { 'x': 2 }, { 'x': 1 }], 'x');

result → [{ 'x': 1 }, { 'x': 2 }]

回答3:

Late to the party but _.unionWith is much better in doing what you want.

var objects = [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }];
var others = [{ 'x': 1, 'y': 1 }, { 'x': 1, 'y': 2 }];

_.unionWith(objects, others, _.isEqual);
// => [{ 'x': 1, 'y': 2 }, { 'x': 2, 'y': 1 }, { 'x': 1, 'y': 1 }]

回答4:

_.unionBy(array1, array2, matcherFn);

回答5:

lodash merge object from arrays

const test1 = [
  { name: 'zhanghong', age: 32, money: 0, size: 12, },
  { name: 'wanghong', age: 20, size: 6 },
  { name: 'jinhong', age: 16, height: 172 },
]

const test2 = [
  { name: 'zhanghong', gender: 'male', age: 14 },
  { name: 'wanghong', gender: 'female', age: 33 },
  { name: 'lihong', gender: 'female', age: 33 },
]

const test3 = [
  { name: 'meinv' },
]

const test4 = [
  { name: 'aaa' },
]

const test5 = [
  { name: 'zhanghong', age: 'wtf' },
]

const result = mergeUnionByKey(test1, test2, test3, test4, [], test5, 'name', 'override')

function mergeUnionByKey(...args) {

  const config = _.chain(args)
    .filter(_.isString)
    .value()

  const key = _.get(config, '[0]')

  const strategy = _.get(config, '[1]') === 'override' ? _.merge : _.defaultsDeep

  if (!_.isString(key))
    throw new Error('missing key')

  const datasets = _.chain(args)
    .reject(_.isEmpty)
    .filter(_.isArray)
    .value()

  const datasetsIndex = _.mapValues(datasets, dataset => _.keyBy(dataset, key))

  const uniqKeys = _.chain(datasets)
    .flatten()
    .map(key)
    .uniq()
    .value()

  return _.chain(uniqKeys)
    .map(val => {
      const data = {}
      _.each(datasetsIndex, dataset => strategy(data, dataset[val]))
      return data
    })
    .filter(key)
    .value()

}

console.log(JSON.stringify(result, null, 4))

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

回答6:

Compare objects using a key property:-

_.unionBy(array1,array2,'propname');

Compare objects using all key property:-

_.unionWith(array1,array2, _.isEqual);

Compare objects using a string key property in case insensitive way:-

_.unionWith(array1,array2, function(obj,other){ return obj.propname.toLowercase() === other.propname.toLowercase(); });

propname is name of key property of your object.

来源：https://stackoverflow.com/questions/29320817/lodash-union-of-arrays-of-objects

标签

javascript

lodash