简单的凯撒加解密，移位算法

caesar-chipper.js

/**
 * 凯撒加解密
 */

// 这里的 26 是必须的，否则导致解密溢出
const num = ~~(Math.random() * 100) % 26

const event = "simple world!"

const MIN = "A".charCodeAt(0)
const MAX = "Z".charCodeAt(0)

let eventR = String.fromCharCode.apply(
    null,
    event
        .toUpperCase()
        .split("")
        .map(e => {
            const charCode = e.charCodeAt(0)
            if (charCode >= MIN && charCode <= MAX) {
                return ((charCode + num - MIN) % 26) + MIN
            } else {
                return charCode
            }
        }),
)
console.log("eventR:", eventR)

let ret = String.fromCharCode.apply(
    null,
    eventR
        .toUpperCase()
        .split("")
        .map(e => {
            const charCode = e.charCodeAt(0)
            if (charCode >= MIN && charCode <= MAX) {
                // charCode = 65
                return ((charCode - MIN - num * 1 + 26) % 26) + MIN
            } else {
                return charCode
            }
        }),
)
console.log("ret:", ret)