gistfile1.js

function say(textOrOptions) {
  if (typeof textOrOptions === 'string') {
    // it's a string
  } else {
    // it's something else
  }
}
 
function say(one, two) {
  var text;
  var voice;
  if (!two) {
    text = one; 
  } else {
    voice = one;
    text = two;
  }
}