Synchronized scrolling using jQuery?

Question

I am trying to implement synchronized scrolling for two DIV with the following code.

DEMO

$(document).ready(function() {
    $(\"#div1\"         


        

Answer 1

Runs like clockwork (see DEMO)

$(document).ready(function(){

  var master = "div1"; // this is id div
  var slave = "div2"; // this is other id div
  var master_tmp;
  var slave_tmp;
  var timer;

  var sync = function ()
  {
    if($(this).attr('id') == slave)
    {
      master_tmp = master;
      slave_tmp = slave;
      master = slave;
      slave = master_tmp;
    }

    $("#" + slave).unbind("scroll");

    var percentage = this.scrollTop / (this.scrollHeight - this.offsetHeight);

    var x = percentage * ($("#" + slave).get(0).scrollHeight - $("#" + slave).get(0).offsetHeight);

    $("#" + slave).scrollTop(x);

    if(typeof(timer) !== 'undefind')
      clearTimeout(timer);

    timer = setTimeout(function(){ $("#" + slave).scroll(sync) }, 200)
  }

  $('#' + master + ', #' + slave).scroll(sync);

});

Answer 2

This is what I'm using. Just call the syncScroll(...) function with the two elements you want to synchronize. I found pawel's solution had issues with continuing to slowly scroll after the mouse or trackpad was actually done with the operation.

See working example here.

// Sync up our elements.
syncScroll($('.scroll-elem-1'), $('.scroll-elem-2'));


/***
*   Synchronize Scroll
*   Synchronizes the vertical scrolling of two elements.
*   The elements can have different content heights.
*
*   @param $el1 {Object}
*       Native DOM element or jQuery selector.
*       First element to sync.
*   @param $el2 {Object}
*       Native DOM element or jQuery selector.
*       Second element to sync.
*/
function syncScroll(el1, el2) {
  var $el1 = $(el1);
  var $el2 = $(el2);

  // Lets us know when a scroll is organic
  // or forced from the synced element.
  var forcedScroll = false;

  // Catch our elements' scroll events and
  // syncronize the related element.
  $el1.scroll(function() { performScroll($el1, $el2); });
  $el2.scroll(function() { performScroll($el2, $el1); });

  // Perform the scroll of the synced element
  // based on the scrolled element.
  function performScroll($scrolled, $toScroll) {
    if (forcedScroll) return (forcedScroll = false);
    var percent = ($scrolled.scrollTop() / 
      ($scrolled[0].scrollHeight - $scrolled.outerHeight())) * 100;
    setScrollTopFromPercent($toScroll, percent);
  }

  // Scroll to a position in the given
  // element based on a percent.
  function setScrollTopFromPercent($el, percent) {
    var scrollTopPos = (percent / 100) *
      ($el[0].scrollHeight - $el.outerHeight());
    forcedScroll = true;
    $el.scrollTop(scrollTopPos);
  }
}