Function Properties (instead of global variables to store invokation values).

FunctionProperties.js

/* 
instead of declaring global variables.
var counter = 0;
$(document).on("click", function(){
  console.log(counter);
  counter++;
});
*/
 
$(document).on("click", function handler(){
  handler.counter = ("counter" in handler) ? handler.counter : 0;
  console.log(handler.counter);
  handler.counter++;
});