Removing duplicates from two arrays in javascript based on a single attribute

Question

I have two arrays in javascript, where i want to do two different operations

Map an attribute upon each element in each lists
filter out none unique values based on an attribute

I have this function so far

export function generateDisplayedLabels(systemLabels, masterState){
  const mappedSystemlabels = systemLabels.map(label => Object.assign(label, {type: "system"}))
  const mappedMasterlabels = masterState.map(label => Object.assign(label, {type: "master"}))
  const displayedLabels = _.union(mappedSystemlabels, mappedMasterState);
  return displayedLabels

}

This would work except for the fact, that whenever i map over the objects in the beginning, the "unique" elements are no longer unique, because they have another attribute mapped upon it. Is there a time efficient way, that i can filter out the none unique elements, ignoring the attribute, that have been mapped onto it.

Please visit the help center, take the tour to see what and How to Ask. Do some research, search for related topics on SO; if you get stuck, post a minimal reproducible example of your attempt, noting input and expected output using the [<>] snippet editor. — mplungjan
– mplungjan, Commented Jun 25, 2020 at 8:52
You could use _.unionBy which takes a function as a second parameter which lets you choose a field or value by which the uniqueness is computed. — cbr
– cbr, Commented Jun 25, 2020 at 8:54

MUHAMMAD ILYAS · Accepted Answer · 2020-06-25 09:23:15Z

2

let ar1 = [
  {
    id: 1,
    name: 'stack',
  },
  {
    id: 2,
    name: 'react',
  },
];

let ar2 = [
  {
    id: 1,
    name: 'javascript',
  },
  {
    id: 2,
    name: 'overflow',
  },
 {
    id: 2,
    name: 'react',
  },
];

console.log(_.unionBy(ar1, ar2, 'id'));
console.log("======");
console.log(_.unionBy(ar1, ar2, 'name'));

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.15/lodash.min.js"></script>

answered Jun 25, 2020 at 9:23

MUHAMMAD ILYAS

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