Final Exam 02. Song Encryption

function solve(input) {
    for (let line of input) {
        if (line === 'end') {
            break;
        }
        let pattern = /(?<artist>^[A-Z][a-z'|\s]+[a-z]*):(?<song>[A-Z\s]+)$/gm;
        let result = pattern.exec(line);
        if (result) {
            let artist = result.groups.artist;
            let song = result.groups.song;
            let key = artist.length;
            let songAndArtist = artist + song;
            songAndArtist = songAndArtist
                .split('')
                .map(function (e) {

                    if (e === " ") {
                        return e = ' ';
                    } else if (e === "'") {
                        return e = "'";
                    } else {
                        let updatedKey = e.charCodeAt(0) + key;
                        if (updatedKey > 'Z'.charCodeAt(0) && e.charCodeAt(0) <= 'Z'.charCodeAt(0)) {

                            let difference = updatedKey - 'Z'.charCodeAt(0);
                            updatedKey = 64 + difference;
                            return e = String.fromCharCode(updatedKey);

                        } else if (updatedKey > 'z'.charCodeAt(0)) {
                            let difference = updatedKey - 'z'.charCodeAt(0);
                            updatedKey = 96 + difference;
                            return e = String.fromCharCode(updatedKey);

                        } else {
                            return e = String.fromCharCode(updatedKey);
                        }
                    }

                });


            songAndArtist.splice(key, 0, '@');
            console.log(`Successful encryption: ${songAndArtist.join('')}`);

        } else {
            console.log("Invalid input!");
        }
    }
}