How can I get a unique array based on object property using underscore

Question

I have an array of objects and I want to get a new array from it that is unique based only on a single property, is there a simple way to achieve this?

Eg.

Answer 1

You can use the _.uniqBy function

var array = [ { id: 1, name: 'bob' }, { id: 2, name: 'bill' }, { id: 1, name: 'bill' },{ id: 2, name: 'bill' } ];

var filteredArray = _.uniqBy(array,function(x){ return x.id && x.name;});

console.log(filteredArray)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.5/lodash.js"></script>

In the above example, filtering is based on the uniqueness of combination of properties id & name.

if you have multiple properties for an object. then to find unique array of objects based on specific properties, you could follow this method of combining properties inside _.uniqBy() method.

Answer 2

In case you need pure JavaScript solution:

var uniqueProperties = {};

var notUniqueArray = [ { id: 1, name: 'bob' }, { id: 1, name: 'bill' }, { id: 1, name: 'bill' } ];


for(var object in notUniqueArray){
   uniqueProperties[notUniqueArray[object]['name']] = notUniqueArray[object]['id'];
}

var uniqiueArray = [];

for(var uniqueName in uniqueProperties){
   uniqiueArray.push(
     {id:uniqueProperties[uniqueName],name:uniqueName});
}

//uniqiueArray

Answer 3

If you prefer to do things yourself without Lodash, and without getting verbose, try this uniq filter with optional uniq by property:

const uniqFilterAccordingToProp = function (prop) {
    if (prop)
        return (ele, i, arr) => arr.map(ele => ele[prop]).indexOf(ele[prop]) === i
    else
        return (ele, i, arr) => arr.indexOf(ele) === i
}

Then, use it like this:

const obj = [ { id: 1, name: 'bob' }, { id: 1, name: 'bill' }, { id: 1, name: 'bill' } ]
obj.filter(uniqFilterAccordingToProp('abc'))

Or for plain arrays, just omit the parameter, while remembering to invoke:

[1,1,2].filter(uniqFilterAccordingToProp())

Answer 4

A better and quick approach

var table = [
  {
    a:1,
    b:2
  },
  {
    a:2,
    b:3
  },
  {
    a:1,
    b:4
  }
];

let result = [...new Set(table.map(item => item.a))];
document.write(JSON.stringify(result));

Found here

Answer 5

If you want to check all the properties then lodash 4 comes with _.uniqWith(sourceArray, _.isEqual)

Answer 6

unique array by id property with ES6:

arr.filter((a, i) => arr.findIndex(b => b.id === a.id) === i);  // unique by id

replace b.id === a.id with the relevant comparison for your case