The following four data structures are new in ECMAScript 6:
A Set is a collection of unique elements of any type.
Set add and delete:
Set size and clear:
It returns boolean value whether an element is present with the given value in the Set object or not.
Converting between Array and Set
You can create an Array from a Set using Array.from or the spread operator.
Set objects store unique values, so any duplicate elements from an Array are deleted when converting.
Array Vs Set
- Checking whether an element exists in an collection using indexOf for arrays is slow.
- Set objects let you delete elements by their value. With an array you would have to splice based on a element's index.
- The value NaN cannot be found with indexOf in array.
- Set objects store unique values, you don't have to keep track of duplicates by yourself.