Basic JavaScript Rock-Paper-Scissors game not working properly

Question

I need a bit of help with a basic JavaScript version of Rock-Paper-Scissors I'm working on. I just started learning today and would like to keep the code as intact as possible, if possible.

The main problem I'm having is with the loop. It continues despite me setting 'again' to 'no' (through the prompt). Also, the computer always seems to choose Rock... I have a feeling that I'm just missing something simple:

<html>
<script type="text/javascript">
    var myChoice = "";
    var compChoice = "";
    var again;
    while (again = "yes")
        {
        myChoice = prompt("Do you choose rock, paper or scissors?");
        compChoice = Math.random();
            if (compChoice < 0.33)
                {
                compChoice = "rock";
                }
            else if(compChoice < 0.67)
                {
                compChoice = "paper";
                }
            else
                {
                compChoice = "scissors";
                }
        if (compChoice = myChoice)
            {
            alert("It's a tie!");
            again = prompt("Would you like to play again?(yes/no)");
            }
        else if (compChoice = "rock")
            {
            if(myChoice = "scissors")
                {
                alert("You lose!");
                again = prompt("Would you like to play again?(yes/no)");
                }
            else if (myChoice = "paper")
                {
                alert("You win!");
                again = prompt("Would you like to play again?(yes/no)");
                }
            }
        else if (compChoice = "paper")
            {
            if (myChoice = "rock")
                {
                alert("You lose!");
                again = prompt("Would you like to play again?(yes/no)");
                }
            else if (myChoice = "scissors")
                {
                alert("You win!");
                again = prompt("Would you like to play again?(yes/no)");
                }
            }
        else if (compChoice = "scissors")
            {
            if (myChoice = "rock")
                {
                alert("You win!");
                again = prompt("Would you like to play again?(yes/no)");
                }
            else if (myChoice = "paper")
                {
                alert("You lose!");
                again = prompt("Would you like to play again?(yes/no)");
                }
            }
        };
</script>
</html>

*sidenote:* The probability of Rock, Paper & Scissor is not equal. Why don't you use a random number, then use the result of `random_number % 3 `? — Raptor, Jul 15 '13 at 02:50
http://stackoverflow.com/questions/22623331/rock-paper-scissors-lizard-spock-in-javascript/22624288#22624288 — Mke Spa Guy, Mar 25 '14 at 17:58

Arun P Johny · Accepted Answer · 2013-07-15T02:59:00.727

You are using = instead of == in the while statement and same in all the if statements also

= is the assignment operator, while == is the comparison operator

var myChoice = "";
var compChoice = "";
var again;
do 
{
    myChoice = prompt("Do you choose rock, paper or scissors?");
    compChoice = Math.random();
    if (compChoice < 0.33)
    {
        compChoice == "rock";
    }
    else if(compChoice < 0.67)
    {
        compChoice = "paper";
    }
    else
    {
        compChoice == "scissors";
    }
    if (compChoice == myChoice)
    {
        alert("It's a tie!");
    }
    else if (compChoice == "rock")
    {
        if(myChoice == "scissors")
        {
            alert("You lose!");
        }
        else if (myChoice == "paper")
        {
            alert("You win!");
        }
    }
    else if (compChoice == "paper")
    {
        if (myChoice == "rock")
        {
            alert("You lose!");
        }
        else if (myChoice == "scissors")
        {
            alert("You win!");
        }
    }
    else if (compChoice == "scissors")
    {
        if (myChoice == "rock")
        {
            alert("You win!");
        }
        else if (myChoice == "paper")
        {
            alert("You lose!");
        }
    }
    again = prompt("Would you like to play again?(yes/no)");

}while (again == "yes");

Demo: Fiddle

Thanks for the quick reply! I followed this advice, but now the script won't run (at least the initial prompt won't appear). Any ideas? — Blawdfire, Jul 15 '13 at 02:56
@Blawdfire you can find another version at http://jsfiddle.net/arunpjohny/K3n7f/3/ — Arun P Johny, Jul 15 '13 at 03:09

score 1 · Answer 2 · answered Jul 15 '13 at 02:50

1

One major issue is that you are assigning values instead of comparing values in multiple places.

a = 2 // assigns a to value 2, and evaluates to true
a == 2 // compares a to 2, only evaluates to true if a has value 2

answered Jul 15 '13 at 02:50

Coin_op

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Basic JavaScript Rock-Paper-Scissors game not working properly

2 Answers2