More efficient choice comparison for Rock Paper Scissors

Question

This is an ongoing school project that I would like to improve. The point is to make the code as efficient (or short) as possible. I would like to reduce it by finding an al

Answer 1

I removed some of your variables and combined some, just to make it shorter. I also got rid of the bulk of the if/else since it's not really needed here. For more info on how a switch works, check out https://javascript.info/switch.

I also changed up your choices so that you can add multiple win or loss conditions for each choice, in case you wanted to upgrade to Rock,Paper,Scissors,Lizard,Spock ( https://www.youtube.com/watch?v=cSLeBKT7-s ).

// Set up our various choices, how they rank, and their action (can also be array if desired).
const choices = {
    Rock     : { win:["Scissors"]        , action:"beats" } ,
    Paper    : { win:["Rock"]            , action:"beats"  } ,
    Scissors : { win:["Paper"]           , action:"cuts" } ,
    Spock    : { win:["Rock","Scissors"] , action:"beats" }
} ;

// Use the keys in choices as our selectable items.
const weapons = Object.keys(choices) ;

// Our basic intro.
const rps = prompt("Welcome to Rock, Paper, Scissors. Would you like to play?" + '\n' + "If you do, enter number 1." + '\n' + "If you don't, enter number 2.");

// Set the computer choice.
const chosenOne = weapons[Math.floor(Math.random()*3)];

// This is an example of your switch.
switch (rps) {
  case "1" : // Since we used text input, we have to evaluate for a text "number".
      alert("Remember:" + '\n' + " - Rock beats the scissors" + '\n' + " - Paper beats the rock" + '\n' + " - The scissors cut the paper");

     // Make your choice.
     let weapon = prompt("Make your choice:" + '\n' + weapons, "");
     // Is our choice valid?
     if ( !weapons.includes(weapon) ) { 
         alert("Invalid choice. Closing Game."); break; 
     } else {
         alert("You chose: " + weapon + '\n' + "The computer chose: " + chosenOne);
     }
     // Did I win?
     alert( compareRPS(weapon,chosenOne) ) ;     
  break ; // This will break out of the switch. Otherwise will fall through to next case.

  case "2":    
    alert("Thanks for visiting! See you later.");
  break ;

  default :
    alert("Invalid option. Closing game.");       
  // No break needed here since this is the end of the switch.
}

// I broke the check-you-vs-cpu functionality out into its own function.
function compareRPS(youC,cpuC) {
    if ( youC === cpuC ) {
      return "It's a tie! Try again to win." ;
    }
    if (choices[youC].win.includes(cpuC)) {
      return "You won! " + youC + " " + choices[youC].action + " " + cpuC + "." ;
    } else {
      return "You lost! " + cpuC + " " + choices[cpuC].action + " " + youC + "." ;
    }
}

NOTE: I also switch between const and let. See https://codeburst.io/part-2-var-vs-const-vs-let-69ea73fe76c1 for differences. I mostly use const to indicate a variable I won't change and let to be one that I can (within its proper scope). There's also var, but I didn't need it here.