let id = 1;

​

function checkItOut (fn) {

  if (fn.done) {

    fn.done = id++;

    console.log('Function run #' + fn.done);

  } else {

    fn.done = id++;

    console.log('First function run (' + fn.done + ')');

  }

}

​

function doSomething () {

  // nothing needed here...

}

​

checkItOut(doSomething); // "First function run (1)"

checkItOut(doSomething); // "Function run #2"

checkItOut(doSomething); // "Function run #3"