问Javascript向下滚动到某个部分

EN

function debounce(func, wait = 20, immediate = true) {
    let timeout
    return function() {
      let context = this,
        args = arguments
      let later = function() {
        timeout = null
        if (!immediate) func.apply(context, args)
      }
      let callNow = immediate && !timeout
      clearTimeout(timeout)
      timeout = setTimeout(later, wait)
      if (callNow) func.apply(context, args)
    }
  }

  const images = document.querySelectorAll('img')

  function checkSlide(e) {
    images.forEach(img => {
      const slideInAt = window.scrollY + window.innerHeight - img.height / 2
      const imageBottom = img.offsetTop + img.height
      const isHalfShown = slideInAt > img.offsetTop
      const isNotScrolledPast = window.scrollY < imageBottom
      if (isHalfShown && isNotScrolledPast) {
        img.classList.add('active')
      } else {
        img.classList.remove('active')
      }
    })
  }

  window.addEventListener('scroll', debounce(checkSlide))

let targets = document.querySelectorAll('.target');

window.addEventListener("scroll", function(){
  let doc = document.documentElement;
  let top = (window.pageYOffset || doc.scrollTop)  - (doc.clientTop || 0);

  let windowHeight = window.innerHeight;

  for (i = 0; i < targets.length; ++i) {
    let target = targets[i];
    if(target.offsetTop < (top + (windowHeight/2))) {
      target.classList.add("visible");
    }
    else {
      target.classList.remove("visible");
    }
  }
});