function Encrypt() {

let plainText = document.getElementById("plain-text").value;

let key = parseInt(document.getElementById("key").value);

let cipheredText = "";

for( var position = 0; position < plainText.length; position++) {

var letter = plainText[position];

if(letter.match(/[a-z]/i)){

var code = parseInt(plainText.charCodeAt(position));

if (code >= 65 && code <= 90) {

letter = String.fromCharCode(((code - 65 + key) % 26) + 65);

}

else if (code >= 97 && code <= 122) {

letter = String.fromCharCode(((code - 97 + key) % 26) + 97);

}

}

cipheredText += letter;

}

document.getElementById("encrypted-text").innerHTML = cipheredText;

}