How to remove duplicate characters and combine strings

Question

I currently have a function

function longest(s1,s2) {
return s1.concat(s2)
.split(“”)
.sort()
.join()
}

How can I edit this function to remove duplicate characters from a string?

Answer 1

https://www.sololearn.com/learn/9639/?ref=app

Answer 2

thanks but im not sure how to amend the code to remove the duplicate characters i thought it was the .filter() function but i cant see where in the above code i would write it?