imitation game - final exam - fundamentals

function game(input) {
    let message = input.shift();
   // console.log(message);
   let line = input.shift();
   while (line != "Decode") {
       let [command, firstArgument, secondArgument] = line.split("|");

       switch (command) {
           case "Move":
               let indexEnd = Number(firstArgument);
               let valid = indexEnd >= 0 && indexEnd <= message.length;
               if (valid) {
                   let newString = message.split('')
                   newString = [...newString.slice(+indexEnd), ...newString.slice(0, +indexEnd)]
                   message = newString.join('');
               }

               break;
            case "Insert":
                let index = Number(firstArgument);
                let value = Number(secondArgument);
        let validation = index >= 0 && index <= message.length;
        if (validation) {
            let newStr = message.split('')
            newStr.splice(+index, 0, value)
            message = newStr.join('')
        }
                break;
           case "ChangeAll":
           let subStr = firstArgument;
           let replacement = secondArgument;
           while(message.includes(message)){

            message = message.replace(subStr,replacement);
            }

               break;
       }
       line = input.shift();
   }
   console.log(`The decrypted message is: ${message}`);
}

game([
    'owyouh',
    'Move|2',
    'Move|3',
    'Insert|3|are',
    'Insert|9|?',
    'Decode']
  );