Pattern to execute a callback after a function is called a certain number of times

gistfile1.js

function counter(times, callback) {
  var ct = 0;
  return function() {
    ct++;
    if (ct === times)
      callback();
  };
};

// register a counter function
var f = counter(3, function() {
  alert('lol');
});

f(); // nothing happens
f(); // more nothing
f(); // alerts 'lol'