Get all non-unique values (i.e.: duplicate/more than one occurrence) in an array

Question

I need to check a JavaScript array to see if there are any duplicate values. What\'s the easiest way to do this? I just need to find what the duplicated values are - I don\'

Answer 1

Following logic will be easier and faster

// @Param:data:Array that is the source 
// @Return : Array that have the duplicate entries
findDuplicates(data: Array): Array {
        return Array.from(new Set(data)).filter((value) => data.indexOf(value) !== data.lastIndexOf(value));
      }

Advantages :

1. Single line :-P
2. All inbuilt data structure helping in improving the efficiency
3. Faster

Description of Logic :

1. Converting to set to remove all duplicates
2. Iterating through the set values
3. With each set value check in the source array for the condition "values first index is not equal to the last index" == > Then inferred as duplicate else it is 'unique'

Note: map() and filter() methods are efficient and faster.