Progress option in fadeout jquery

I am trying to use the progress option for the fadeOut animation in jquery. I have no idea how to properly implement it though. One of the versions I tried based on this answer is:

$(window).on("load", function() {
  var timer = 1000;

  $(".loader-wrapper").fadeOut(timer, progress)

  function progress(progress, progressNb, remaining) {
    console.log(progressNb)
  }
});

But I get undefined in the console.

Most of the other answers I found were about starting something after the fadeout animation (example), but this is not what I want.

Your current fadeOut function call uses the .fadeOut( [duration ] [, complete ] ) signature that accepts only duration and complete callback function. But as you need more options you must use the .fadeOut( options ) signature as follows in order to configure/play with the different options:

$(window).on("load", function() {
  var timer = 1000;

  $(".loader-wrapper").fadeOut({duration: timer, progress: progress})

  function progress(progress, progressNb, remaining) {
    console.log(progressNb)
  }
});