是否有窗口元素可用于确定您何时在网页的底部？

Question

我正在尝试创建一个进度栏，以显示某人在网页上有多远，我还希望用户在单击进度栏后能够跳到下一节。当前有2个问题：

1。）Progress Bar只有在您已经滚动的情况下才会将您移至下一节。我希望它能够向前转到每个部分，无论用户是否滚动。

2.）当您进入最后一部分时，按钮不会将您移回网页顶部的第一部分。

[JavaScript]

const progressBarFN = () => {
    //ProgressBarFN Variables
    const pageViewportHeight = window.innerHeight;
    const pageHeight = document.documentElement.scrollHeight;
    const scrolledPortion = window.pageYOffset;
    const scrolledPortionDegree = (scrolledPortion / (pageHeight - pageViewportHeight)) * 360;
    const scrollBool = scrolledPortion + pageViewportHeight === pageHeight;
    //End of Variables

    //Progress Bar Tracker Conditional
    halfCircle.forEach(el => {
        el.style.transform = `rotate(${scrolledPortionDegree}deg)`;

        if(scrolledPortionDegree >= 180) {
            halfCircle[0].style.transform = 'rotate(180deg)';
            halfCircleTop.style.opacity = "0";
        } else {
            halfCircleTop.style.opacity = "1";
        }
    });
    //End of Progress Bar Tracker Conditional
    
    //Progress Bar Click
    progressBar.onclick = e => {
        e.preventDefault();

        //Progress Bar OnClick Variables
        const sectionPositions = Array.from(sections).map(section => scrolledPortion + section.getBoundingClientRect().top);

        const position = sectionPositions.find(sectionPosition => {
            return sectionPosition > scrolledPortion;
        });
        //End of Progress Bar OnClick Variables

       //OnClick conditional
        if (scrollBool) {
            window.scrollTo(0,0);
        } else {
            window.scrollTo(0,position);
        };
       //End of OnClick Conditional 
    };
}
progressBarFN();

• Sidenote：我在声明后并在滚动EventObjectListEner中声明了此功能。

我相信，对于progressbarfn的初始变量，这个问题需要解决。尤其是我的滚动变量。