Is there a way to make my Rock, Paper, Scissors game more concise?
Just build an object with the associativity.

// what wins to what
var winsTo = {
  'rock': 'scissors',
  'paper': 'rock',
  'scissors': 'paper',
};

// invalid selected
if (!(choice1 in winsTo &amp;&amp; choice2 in winsTo)) {
  alert("bad choice !");
  return;
}

// same choice =&gt; equality
if (choice1 == choice2) {
  alert("Equality!");
} else if (winsTo[choice1] == choice2) {
  alert("choice1 won!");
} else {
  alert("choice2 won!");
}