The best way to remove duplicate strings in an array

Question

We have managed to create the script below to remove any duplicate strings from an array. However, it is important that we keep the order of the array for when angular loops through them on an ng-repeat. In addition, we want the remaining elements to keep the same index.

scope.feedback = _.map(_.pluck(item.possibleAnswers, 'feedback'), function (element, index, collection) {
    return collection.slice(0, index).indexOf(element) === -1 ? element : '';
});

This code above works however we feel like there must be a more simple solution to our problem than this. Has anyone else had a similar problem and come up with a better solution?

Answer 1

Variant with reduce https://jsfiddle.net/58z7nrfy/1/

var a = [1,2,3,1,2,3,2,2,3,4,5,5,12,1,23,4,1];

var b = a.reduce(function(p,c,i,a){
  if (p.indexOf(c) == -1) p.push(c);
  else p.push('')
  return p;
}, [])
console.log(b)

[1, 2, 3, "", "", "", "", "", "", 4, 5, "", 12, "", 23, "", ""]

Answer 2

Apart from the answers mentioned, you can also use lodash union function like this:

let duplicates = ['Hello', 'Hi', 'Hello'];
let uniques = _.union(duplicates);

Uniques will be: ["Hello", "Hi"]

Answer 3

If the target browsers support spread operator then try in your console:

[...new Set(['3','1','1','5'])]
// ['3','1','5']

Or if browser support Array.from you could also write:

Array.from(new Set(['3','1','1','5']))
// ['3','1','5']