RPS.js

// Initializing Variables
function RPSLS()
{
    var choices = [
		{
			name: "rock",
			beats: {
				"scissors": "crushes",
				"lizard": "crushes"
			}
		},
		{
			name: "paper",
			beats: {
				"spock": "disproves",
				"rock": "covers"
			}
		},
		{
			name: "scissors",
			beats: {
				"paper": "cuts",
				"lizard": "decapitates"
			}
		},
		{
			name: "lizard",
			beats: {
				"spock": "poisons",
				"paper": "eats"
			}
		},
		{
			name: "spock",
			beats: {
				"scissors": "smashes",
				"rock": "vaporizes"
			}
		}
	];
     
	function play()
	{
		var cpuChoice = choices[ Math.floor( Math.random() * choices.length ) ];
		var i;
		var details;
		var userChoice = prompt("Do you choose rock, paper or scissors, lizard, or spock?");
		
		while( true )
		{
			for(i=0; i<choices.length; i++ ) {
				if( choices[i].name === userChoice ) {
					userChoice = choices[i];
					break;
				}
			}
			
			// it's not a string
			if( userChoice.name ) {
				break;
			}
				
			userChoice = prompt("You did not select rock, paper, scissors, lizard, or spock. Please try again.");
		}

		if( cpuChoice == userChoice ) {
			return "The result is a tie!";
		}

		details = {
			youPicked: userChoice.name,
			cpuPicked: cpuChoice.name,
			how: cpuChoice.beats[userChoice.name],
			cpuWins: true
		};

		if( ! details.how ) {
			details.how = userChoice.beats[cpuChoice.name];
			details.cpuWins = false;
		}

		return "You picked " + details.youPicked + ". " +
			   "Computer picked " + details.cpuPicked + ". " +
			   (details.cpuWins ? details.cpuPicked : details.youPicked ) + " " +
			   details.how + " " +
			   (details.cpuWins ? details.youPicked : details.cpuPicked) + ". " +
			   "You " + (details.cpuWins ? "lose" : "win") + ".";
	}

	return { play: play };
}
 
// not including the prompt stuff
// to play a new game
var rpsls = new RPSLS();
rpsls.play();