Puck.js with LDR - how to deal with light that is always on?

ok... I think I get it now =) thank you for your patience - my brain must be functioning in another way =) But running through it I feel I still dont get it =)
Lets imagine that LED is not stuck and its functioning as needed. And LED is currently OFF during the time this check is done.
Running through this function makes it:
pulledUp=true
first IF is not fired up, as pulledUP variable is true
second IF is fired up and sets pulledUP variable to true again
third IF is not fired up as pulledUP variable is true

Now, there is a brief pulse of LED light, which is a normal meter functioning, but outside the function's 10second loop.
How does my setWatch function work if we did not set the pinMode for D2 to be input_pullup?

  setWatch(function(e) {
    if (!pulledUp) return;
    c.inc(1);
    pulseTotal++;
    update();
    if (LEDStatus==1){
      digitalPulse(LED1,1,1); // show activity
    }
  }, D2, { repeat:true, edge:"falling" });

I keep wanting to change

if (!pulledUp) pinMode(D2,"input_pullup");

to

if (pulledUp) pinMode(D2,"input_pullup");

Just dont understand how it works without changing the pinMode if pulledUp variable is staying true on the "unstuck" day