var userChoice = prompt("Do you choose rock, paper or scissors?");

var computerChoice = Math.random();
if (computerChoice < 0.34) {
    computerChoice = "rock";
} else if(computerChoice <= 0.67) {
    computerChoice = "paper";
} else {
    computerChoice = "scissors";
}

console.log("Computer chose: " + computerChoice);
console.log("You chose: " + userChoice);

var compare = function(choice1, choice2) {
    if(choice1 === choice2) {
        return "The result is a tie!";
    }
    else if(choice1 === "rock") {
        if(choice2 === "scissors") {
            return "rock wins";
        }
        else {
            return "paper wins";
        }
    }
    else if(choice1 === "paper") {
        if(choice2 === "rock") {
            return "paper wins";
        }
        else {
            return "scissors wins";
        }
    }
    else if(choice1 === "scissors") {
        if(choice2 === "rock") {
            return "rock wins";
        }
        else {
            return "scissors wins";
        }

    }
};

console.log(compare(userChoice, computerChoice));

var invalidChoice = function(userChoice) {
    if(userChoice !== "rock") {
        return "Your choice is invalid!";
    }
    else if(userChoice !== "paper") {
        return "Your choice is invalid!";
    }
    else if(userChoice !== "scissors") {
        return "Your choice is invalid!";
    }
};

console.log(invalidChoice(userChoice));