Give me an idea how to implement a Caesar cipher in JS?

Question

JavaScript

It is necessary to implement a script that would encrypt the text using the Caesar Cipher (each letter of the text is shifted by +-n characters to the right / left relative to its position in the alphabet). I am just starting to program, so only one implementation idea was born - to receive a unicode character and shift accordingly.
My way of implementation seems to me govnokoda.
codepen.io/heyjoe/pen/wKKgeG
Please tell me other ways to implement this script.

Answer 1

1. Create a string containing the alphabet
   codepen.io/ptrvch/pen/VvvPdo

Answer 2

The idea is to make a list of all letters that can be converted.
If someone enters a string with characters outside of this list, such as hieroglyphs, then they will not be shifted, because they are not in the list.

Answer 3

You distill the entire string into a letter-by-character array and iterate through its elements
For each character, set a condition check and replace the contents of the array element with the desired character
And reverse mirror decoding operation
But there is no cryptographic strength at all
Because there is a frequency of using characters in each language, it has its own