var moves = {1 : "rock", 2 : "paper", 3 : "scissors"}

function rand(maximum) {
    return moves[Math.ceil(Math.random() * maximum)]
}

while (true) {
    var enemyDecision = rand(3);
    var myDecision = prompt("Rock, paper, or scissors?").toLowerCase()
    console.log(
        myDecision == enemyDecision && "Tie!  You both chose " + myDecision ||
        (
            myDecision == "rock" && enemyDecision == "paper" ||
            myDecision == "paper" && enemyDecision == "scissors" ||
            myDecision == "scissors" && enemyDecision == "rock"
        ) && "You lose! Opponent chose " + enemyDecision + " and you chose " + myDecision ||
        "You win! Opponent chose " + enemyDecision + " and you chose " + myDecision
    )
}