Caesar cipher written in JavaScript. This only works for A-Z. Lowercase and symbols is not shifted intentionally.

caesar_cipher.js

// This only works for A-Z. Lowercase and symbols will not be shifted.
let str = "UAMG! VJKU QPNA YQTMU HQT C-B."
let shift = -2

let arr = Array.from(str).map((item) => item.charCodeAt(0))
arr = arr.map((item) => {
    if (item >= 65 && item <= 90) { // is A-Z
        let temp = item + shift
        if (!(temp >= 65 && temp <= 90)) { // result out of bound
            if (shift < 0) { return temp + 26 } // if shift is neg
            else { return temp - 26 }
        } else { // result in bound
            return temp
        }
    } else { // not in A-Z, return the original value
        return item
    }
})

console.log(
    arr.map((item) => String.fromCharCode(item)).join("")
)