script

let alphabetString = 'qwertyuiopasdfghjklzxcvbnm1234567890 QWERTYUIOP{}ASDFGHJKL:"ZXCVBNM<>?/;\'[].,!@#$%^&*()_+\\=-|`йцукенгшщзхъфывапролджэячсмитьбюЙЦУКЕНГШЩЗХЪФЫВАПРОЛДЖЭЯЧСМИИТЬ╔'
let alphabet = Array.from(alphabetString)
let alphabetLength = alphabet.length


function encode(string, shift) {
    let chars = Array.from(string)
        .map(char => alphabet.indexOf(char))
        .map(indexOfChar => (indexOfChar + shift))
        .map(Math.abs)
        .map(indexOfChar => indexOfChar % alphabetLength)
        .map(indexOfChar => alphabet[indexOfChar])
    
    return charsToString(chars) 
}

function decode(string, shift) {
    let negativeShift = 0 - shift
    
    console.log(negativeShift)
    
    return encode(string, negativeShift)
}

function charsToString(chars) {
    let res = ""
    
    for (char of chars) {
        res += char
    }
    
    return res
}

let button1 = document.querySelector("#button1")
let button2 = document.querySelector("#button2")
button1.addEventListener("click",function(){
	let text = document.querySelector("#text1").value
	let shift = document.querySelector("#text3").value
	let text1 = encode(text, shift)
	let div = document.createElement("div")
	div.append(text1)
	document.querySelector("#output1").append(div)
})

button2.addEventListener("click",function(){
	let text = document.querySelector("#text2").value	
	let shift = document.querySelector("#text3").value
	let text1 = decode(text, shift)
	let div = document.createElement("div")
	div.append(text1)
	document.querySelector("#output2").append(div)
})

let selector = document.querySelector("#shifrator")

selector.addEventListener("change",function(){
	shifrators = selector.value
})