Removing Duplicates in Arrays

Question

I am trying to pass a function that removes duplicates from an array. It should handle strings, object, integers as well. In my code so far I am showing that it will handle strings but nothing else. How can Imake this function universalto handle numbers,handle arrays,handle objects, and mixed types?

let unique = (a) => a.filter((el, i ,self) => self.indexOf(el) ===i);

In this function I hav unique() filtering to make a new array which checks the element and index in the array to check if duplicate. Any help would be appreciated.

What you consider as duplicates in case of objects, for example? If you need more flexible solution go for: https://lodash.com/docs/4.17.4#uniq For strings and integers, this would be the shortest way to remove duplicates: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set — sinisake, Dec 20 '17 at 00:10
Possible duplicate of [Get all unique values in an array (remove duplicates)](https://stackoverflow.com/questions/1960473/get-all-unique-values-in-an-array-remove-duplicates) — Dexygen, Dec 20 '17 at 00:43

score 0 · Accepted Answer · answered Dec 20 '17 at 00:27

i think the first you should do is to sort the array ( input to the function ). Sorting it makes all the array element to be ordered properly. for example if you have in an array [ 1, 3, 4, 'a', 'c', 'a'], sorting this will result to [ 1 , 3 , 4, 'a', 'a' , 'c' ], the next thing is to filter the returned array.

const unique = a => {
    if ( ! Array.isArray(a) )
        throw new Error(`${a} is not an array`);
    let val = a.sort().filter( (value, idx, array) => 
                 array[++idx] != value
             )
    return val;
}

let array = [ 1 , 5, 3, 2, "d", "q", "b" , "d" ];

unique(array); // [1, 2, 3, 5, "b", "d", "q"]

let obj = { foo: "bar" };

let arraySize = array.length;
array[arraySize] = obj;
array[arraySize++] = "foo";
array[arraySize++] = "baz";
array[arraySize++] = obj;

unique(array); // [1, 2, 3, 5, {…}, "b", "baz", "d", "foo", "hi", "q"]

it also works for all types, but if you pass in an array literal with arrays or objects as one of its element this code will fail

 unique( [ "a", 1 , 3 , "a", 3 , 3, { foo: "baz" }, { foo: "baz" } ] ); // it will not remove the duplicate of { foo: "baz" } , because they both have a different memory address

and you should also note that this code does not return the array in the same order it was passed in , this is as a result of the sort array method

score 0 · Answer 2 · answered Dec 20 '17 at 00:39

0

Try using sets without generics. You can write a function as

Set returnUnique(Object array[]) {
Set set=new HashSet();
  for (Object obj:array) {
     set.add(obj);
}
return set;
}

answered Dec 20 '17 at 00:39

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Removing Duplicates in Arrays

2 Answers2