The Imitation Game JS Fundamentals

function theImitationGame(arr) {
    let message = arr.shift().split(',').toString();

    for (let line of arr) {
        let tokens = line.split('|');
        let command = tokens[0];

        if (command === "Move") {
            let part = message.slice(tokens[1]);
            let subs = message.slice(0, tokens[1]);
            message = part + subs;
        } else if (command === "Insert") {
            message = message.substring(0, tokens[1]) + tokens[2] + message.substring(tokens[1]);
        } else if (command === "ChangeAll") {
            for (let letter of message) {
                if (letter === tokens[1]) {
                    message = message.replace(letter, tokens[2]);
                }
            }
        } else if (command === 'Decode') {
            console.log(`The decrypted message is: ${message}`);
        }
    }
}