Make a program that filters a list of strings and returns a list with only your friends name in it.
If a name has exactly 4 letters in it, you can be sure that it has to be a friend of yours! Otherwise, you can be sure he's not...
Ex: Input = ["Ryan", "Kieran", "Jason", "Yous"], Output = ["Ryan", "Yous"]
i.e.
friend ["Ryan", "Kieran", "Mark"] shouldBe
["Ryan", "Mark"]
function friend(friends){
return friends.filter(el => el.length === 4)
}