Find values in array of object with another array of strings

Question

Requirement - I would like to fetch labels from the array of object if the id exists which will be fetched from another array. If that id don't exists, I would like to return that id from the second array.

var objectVar = [{ id: '1', label: 'One' }, { id: '2', label: 'Two' }, { id: '3', label: 'Three' }];
var arrVar = ['1', '2', '3', '4'];

Here, as 1,2,3 exists I would like to return the labels of it and since 4 doesn't exist in array of object, I would like to return 4. This can be stored in a new Array.

Expected result might look like this -

result = ['One', 'Two', 'Three', '4'];

D M · Accepted Answer · 2022-08-25 14:45:10Z

You want to return something for each value in arrVar, so you probably want Array#map. The function we'll apply to each item will check if the item exists as an id in objectVar.

We'll use Array#find to search objectVar for the object with a matching id.

We'll use the ternary operator to choose whether to return the found object's label or our arrVar number.

var objectVar = [
  { id: '1', label: 'One' }, 
  { id: '2', label: 'Two' },
  { id: '3', label: 'Three' }
];
var arrVar = ['1', '2', '3', '4'];

const output = arrVar.map(i => {
  let found = objectVar.find(o => o.id === i);
  return found ? found.label : i;
});

console.log(output);

This approach is nearly twice as fast as the other proposed answers in a single run. The mapper function approach might be faster if you have to repeatedly test new arrVar arrays against objectVar.

Approach	Ops/s	Result
Mapper function	3,237,444.05	37.43% slower
`Array#map`, `Array#find`	5,174,453.56	Fastest
`Array#filter`	3,453,123.01	33.27% slower

Sakil · Accepted Answer · 2022-08-25 14:36:15Z

0

let objectVar = [{ id: '1', label: 'One' }, { id: '2', label: 'Two' }, { id: '3', label: 'Three' }];
let arrVar = ['1', '2', '3', '4'];
let output = arrVar.map(a => {
    let matched = objectVar.filter(x => x.id == a);
    if(matched.length > 0) {
        return matched[0].label;
    }
    return a;
});
console.log(output)

answered Aug 25, 2022 at 14:36

Sakil

6525 silver badges8 bronze badges

Comments

adiga · Accepted Answer · 2022-08-25 14:36:23Z

0

You could create a mapper object which maps id to the label

const objectVar = [{ id: '1', label: 'One' }, { id: '2', label: 'Two' }, { id: '3', label: 'Three' }],
      arrVar = ['1', '2', '3', '4'],
      labelMapper = Object.fromEntries(objectVar.map(o => [o.id, o.label])),
      output = arrVar.map(n => labelMapper[n] ?? n)

console.log(output)

answered Aug 25, 2022 at 14:36

adiga

35.4k9 gold badges65 silver badges88 bronze badges

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