scrollTo.js

'use strict';
var getOffset = require('../query/offset')
  , height = require('../query/height')
  , getScrollParent = require('../query/scrollParent')
  , scrollTop = require('../query/scrollTop')
  , raf = require('./requestAnimationFrame')
  , getWindow = require('../query/isWindow')

module.exports = function scrollTo( selected, scrollParent, scrollToTop = false ) {
  var offset = getOffset(selected)
    , poff   = { top: 0, left: 0 }
    , list, listScrollTop, selectedTop, isWin
    , selectedHeight, listHeight, bottom;

    if( !selected ) return 

    list          = scrollParent || getScrollParent(selected)
    isWin         = getWindow(list)
    listScrollTop = scrollTop(list)

    listHeight    = height(list, true)
    isWin         = getWindow(list)

    if (!isWin) 
      poff = getOffset(list)

    offset     = {
      top:    offset.top  - poff.top,
      left:   offset.left - poff.left,
      height: offset.height,
      width:  offset.width
    }

    
    selectedHeight = offset.height
    selectedTop    = offset.top  + (isWin ? 0 : listScrollTop)
    bottom         = scrollToTop ? selectedTop + listHeight : selectedTop + selectedHeight;

    listScrollTop = listScrollTop > selectedTop
          ? selectedTop
          : bottom > (listScrollTop + listHeight) 
              ? (bottom - listHeight)
              : listScrollTop

    var id = raf(() => scrollTop(list, listScrollTop))

    return () => raf.cancel(id)
}