Why doesn't the setTimeout delay work in the loop?

Question

JavaScript

You need to smoothly rewind the page to the top by clicking. There is a delay of 100ms in the loop and the current position decreases by 10 pixels with each iteration. When you try to run the page jumps to the top instantly.

var position=window.pageYOffset;
while(position>0)
    {
    setTimeout(function (){window.scrollTo(0,position)}, 100);
    position=position-10;
    }

However, if we add, for example, alert(position); into the body of the loop, you can see that with each iteration, the page actually shifts and the position value actually decreases by 10 pixels. What could be the problem?
UPD: If you set a long delay time (without alert), the page scrolls not instantly, but after a second or two.

Answer 1

And you insert alert into the anonymous function that you pass to the setTimeout call. Everything will become clear right away. It's better to do this:

function smoothScroll() {
    if(window.pageYOffset > 0) {
        window.scrollTo(0, window.pageYOffset - 10);
        setTimeout(smoothScroll, 100);
    }
}

setTimeout(smoothScroll, 100);