Remove 'duplicate' objects from array by comparing sub properties (typescript)

Question

I receive an array of complex objects from the server. I would like to filter the original array to get a new array with unique objects by a sub-property of an each object, i.e :

let arr1 = originalArray;
let arr2 = originalArray.filter((ele, idx, arr) => ....

Now for example, arr1 consists of 3 objects:

firstObj = {
    id: 0,
    Details:
        {
            License: 123456
        },
    name: 'abc'
};
secondObj = {
    id: 1,
    Details:
        {
            License: 131313
        },
    name: 'xcd'
};
thirdObj = {
    id: 2,
    Details:
        {
            License: 123456
        },
    name: 'bcd'
};

So, I want to filter the array so that the newly returned array will consist of only two objects where the 'License' property will be unique, that is, one of the objects with the same 'License' will be removed. Thanks.

mickl · Accepted Answer · 2018-06-03 12:00:26Z

11

You can use array.reduce to loop through source array and add items to result if it does not contain same Details.License

let result = [firstObj, secondObj, thirdObj].reduce((arr, item) => {
    let exists = !!arr.find(x => x.Details.License === item.Details.License);
    if(!exists){
        arr.push(item);
    }
    return arr;
}, []);

answered Jun 3, 2018 at 12:00

mickl

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1 Comment

WasiF Over a year ago

Awsome solution :)

charlietfl · Accepted Answer · 2018-06-03 13:11:49Z

4

If order they occur is not important can pass them into a Map using Licence values as keys.

Map keys must be unique so this will overwrite duplicates as they occur while creating the Map and return last instance of each duplicate

let uniques = [...new Map(data.map(o=>[o.Details.License,o])).values()];


console.log(uniques)

<script>
let data = [{
  id: 0,
  Details: {
    License: 123456
  },
  name: 'abc'
}, {
  id: 1,
  Details: {
    License: 131313
  },
  name: 'xcd'
}, {
  id: 2,
  Details: {
    License: 123456
  },
  name: 'bcd'
}]
</script>

Alternate approach using Array#filter and a Set to track unique values

let licSet = new Set();
let uniques = data.filter(({Details: o}) => !licSet.has(o.License) && licSet.add(o.License));


console.log(uniques)

<script>
  let data = [{
    id: 0,
    Details: {
      License: 123456
    },
    name: 'abc'
  }, {
    id: 1,
    Details: {
      License: 131313
    },
    name: 'xcd'
  }, {
    id: 2,
    Details: {
      License: 123456
    },
    name: 'bcd'
  }]
</script>

edited Jun 3, 2018 at 13:11

answered Jun 3, 2018 at 12:18

charlietfl

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2 Comments

dextercom Over a year ago

Also a great solution, thanks. I should get more accustomed to using the spread operator.

charlietfl Over a year ago

If large data set I believe this would be more performant than using nested find()

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