利用Math.ceil等近似方法是否会影响该滚动动画的精确性?

Question

完整代码及动画运行效果:https://codepen.io/TristanBLG/pen/xWvByO?editors=1010

代码中实现了滚动页面至相应元素的功能,有疑问的地方在于代码利用Math.ceil、Math.round做了一些近似的处理,这是否会影响到页面滚动到对应元素的精确性?涉及到小数总是难以判断.
比如使用Math.ceil处理后会比原始值大0.x,如果要求动画精确一点,这0.x是这个例子中不需要考虑的吗?
为什么有些地方用Math.ceil?而有些地方又用了Math.round?

做了近似处理的地方:

window.scroll(0, Math.ceil((time * (destinationOffsetToScroll - start)) + start))

if(time >= 1 || Math.round(window.pageYOffset) === destinationOffsetToScroll) {}

完整JavaScript代码:

const scrollTo = function({target, duration = 200, callback} = {}){
  if(!target){
    console.error('scrollTo() => You must specify a target.')
    return false
  }
  const targetHref                  = target.getAttribute('href').replace( /^#/ , '')
  const destination                 = document.getElementById(targetHref)
  const start                       = window.pageYOffset
  const startTime                   = 'now' in window.performance ? performance.now() : new Date().getTime()
  const documentHeight              = Math.max(document.body.scrollHeight, document.body.offsetHeight, document.documentElement.clientHeight, document.documentElement.scrollHeight, document.documentElement.offsetHeight)
  const windowHeight                = window.innerHeight || document.documentElement.clientHeight || document.getElementsByTagName('body')[0].clientHeight
  const destinationOffset           = typeof destination === 'number' ? destination : destination.offsetTop
  const destinationOffsetToScroll   = Math.round(documentHeight - destinationOffset < windowHeight ? documentHeight - windowHeight : destinationOffset)

  if('requestAnimationFrame' in window === false) {
      window.scroll(0, destinationOffsetToScroll)
      if(callback) {
          callback()
      }
      return
  }
  
  const scroll = function() {
    const now   = 'now' in window.performance ? performance.now() : new Date().getTime()
    const time  = Math.min(1, ((now - startTime) / duration))
    
    window.scroll(0, Math.ceil((time * (destinationOffsetToScroll - start)) + start))
    
    if(time >= 1 || Math.round(window.pageYOffset) === destinationOffsetToScroll) {
      if(callback) {
        callback()
      }
      return
    }

    requestAnimationFrame(scroll)
  }

  requestAnimationFrame(scroll)
};

const navLink = Array.from(document.querySelectorAll('[href^="#"]'))
  navLink.forEach(el => {
    el.addEventListener('click', function(ev) {
      ev.preventDefault()
      ev.stopPropagation()
      scrollTo({
        duration: 300,
        target: ev.target
      });
    })
})

Answer 1

设置scrollTop包含小数实际会调用Math.floor，设置不了小数，所以多少会有点定位不准，0.几px是少不了