findLetters.js

// Find the Unique Letters

// Create a function that takes a string and returns an array of the letters that occur only once.

// findLetters("monopoly") ➞ ["m", "n", "p", "l", "y"]

// findLetters("balloon") ➞ ["b", "a", "n"]

// findLetters("analysis") ➞ ["n", "l", "y", "i"]

// Notes
// 1 -  The final array should not include letters that appear more than once in the string.
// 2 - Return the letters in the sequence they were originally in, do not sort them.
// 3 - All letters will be in lowercase.