Caesar Cipher - Exercism JavaScript Exercise

Discussion of my solution to the Caesar Cipher exercise on Exercism I used JavaScript to build a Class for encoding and decoding strings. It can accept a single letter for a key and effect the Caesar Cipher. It can accept longer and varying strings to effect the substitution cipher. If a string isn't specified, it will generate a random one that is 100 characters long. This is my first time discussing my study on JavaScript. My composition is stop-start and learning along the way. I think that it will help me to describe what I've built at the end. Tie it together a bit in my mind. If this is helpful to others, then even better. If you would like to share you thoughts on this or on a creative approach that worked for you, then please do!