The Imitation Game [JavaScript]

function theImitationGame(input) {
    let message = input.shift();

    let line = input.shift();

    while (line != "Decode") {
        let tokens = line.split("|");

        let command = tokens[0];

        switch (command) {
            case "Move": {
                let index = Number(tokens[1]);

                let firstPart = message.substring(0, index);
                let secondPart = message.substring(index);

                message = secondPart + firstPart;

                break;
            }
            case "Insert": {
                let index = Number(tokens[1]);

                let firstPart = message.substring(0, index);
                let secondPart = message.substring(index);
                let value = tokens[2];

                message = firstPart + value + secondPart;

                break;
            }
            case "ChangeAll": {
                let subString = tokens[1];
                let replacement = tokens[2];

                message = message.split(subString).join(replacement);

                break;
            }
        }

        line = input.shift();
   }

   console.log(`The decrypted message is: ${message}`);
}