// 左右栏同步滚动
$(document).ready(() => {
  let timeout
  $('div.CodeMirror-scroll, #preview').on('scroll', function callback () {
    clearTimeout(timeout)

    let source = $(this)
    let target = $(source.is('#preview') ? 'div.CodeMirror-scroll' : '#preview')

    target.off('scroll')

    let source0 = source[0]
    let target0 = target[0]

    let percentage = source0.scrollTop / (source0.scrollHeight - source0.offsetHeight)
    let height = percentage * (target0.scrollHeight - target0.offsetHeight)
    target0.scrollTo(0, height)

    timeout = setTimeout(() => {
      target.on('scroll', callback)
    }, 100)
  })
})