Ensures a function is only called once.

once.js

//Once
function once(fn) {
  var done = false;

  return function() {
    return done ? void 0 : ((done = true), fn.apply(this, arguments));
  };
}

var askedOnBlindDate = once(function () {
   return 'sure, why not?';
 });

console.log(askedOnBlindDate());
console.log(askedOnBlindDate());