JS script to play "Rock, paper, scissors, lizard, spock"

RPSLS.js

function get_random(topLim) {
    return Math.round(Math.random()*topLim);
}

var RPSLS = function() {

  var ret = {};

	var map = {

		"rock" : {
			"scissors" : "crushes",
			"lizard" : "crushes"
		},
		"scissors" : {
			"paper" : "cuts",
			"lizard" : "decapitates"
		},
		"spock" : {
			"scissors" : "smashes",
			"rock" : "vaporizes"
		},
		"lizard" : {
			"spock" : "poisons",
			"paper" : "eats"
		},
		"paper" : {
			"spock" : "disproves",
			"rock" : "covers"
		}
	}

	// TODO: Validate this against the map object
	var userChoice = prompt("Rock, paper, scissors, lizard, spock?");

	// Randomly selecting correct value for computerChoice
	var computerChoice = get_random(Object.keys(map).length - 1);
	computerChoice = Object.keys(map)[computerChoice];


	// Function that compares the two values
	ret.compare = function() {
		
		if ( userChoice === computerChoice ) {
			return "The result is a tie!";
		}


		// if the userChoice object contains the computerChoice, the user wins
		if ( map[userChoice].hasOwnProperty(computerChoice) ) {
			return "You win! " + userChoice + " " + map[userChoice][computerChoice] + " " + computerChoice;
		} else {
			return "You lose! " + computerChoice + " " + map[computerChoice][userChoice] + " " + userChoice;
		}
	}

	return ret;

}();



RPSLS.compare();