Talk In Code

Having a Marquee on a web page is a nightmare from an XHTML validation point of view, so here is a neat function that will produce the same effect as a vertical scrolling marquee, that passes XHTML validation, and built entirely from JavaScript and CSS.

Vertical Scrolling

Take the following HTML code. Don’t worry about reading it. It is just 7 p tags (2 of which act as spacers) contained within a div tag.
<div id="marquee_replacement" onmouseout="startit();" onmouseover="stop();">
<p class="spacer"></p>
<p>Lorem ipsum dolor sit amet consectetur enim proident in elit est. Culpa sit ad aliquip laboris sit ad tempor in dolore proident. Ut ut deserunt laboris ut exercitation sit consectetur nisi sunt incididunt. Nisi non et qui adipisicing labore tempor consequat anim id dolore. Veniam velit aliquip laborum. cillum dolor amet sed dolore laborum. in. Magna deserunt veniam anim ut deserunt est ut ut.</p>
<p>Aute enim quis duis exercitation magna cupidatat ullamco duis voluptate ullamco. Ad eu est in commodo occaecat mollit officia sit elit excepteur. Elit sint duis excepteur reprehenderit consequat cupidatat quis esse occaecat elit. Officia tempor laborum. dolore dolore nulla ea adipisicing pariatur irure deserunt. Enim ullamco mollit ut eu lorem elit ex sit cillum pariatur. Laboris laboris tempor ex ad officia eu.</p>
<p>Elit est laboris nisi nostrud incididunt exercitation qui in excepteur eiusmod. Exercitation eu occaecat mollit amet esse enim consectetur non veniam occaecat. Ea occaecat commodo dolore sunt ullamco veniam incididunt aliqua labore minim. Velit et amet nulla consectetur enim eiusmod enim ut in cupidatat. Velit do excepteur dolor sed nostrud cillum ad ea veniam sint. Culpa ex sed esse exercitation sed do in lorem ea proident. Ullamco labore.</p>
<p>Eiusmod id quis exercitation officia sit aliquip enim in in aliquip. Lorem adipisicing officia elit pariatur proident ut irure aute id dolor. Tempor cillum non dolore lorem enim in velit et pariatur consequat. Excepteur ad ex fugiat est esse dolore consectetur ut ut dolor. Mollit consequat culpa laborum. aliquip sunt nostrud dolore consequat cillum labore. Dolor officia lorem do sunt nostrud aliqua velit voluptate.</p>
<p>Eiusmod id quis exercitation officia sit aliquip enim in in aliquip. Lorem adipisicing officia elit pariatur proident ut irure aute id dolor. Tempor cillum non dolore lorem enim in velit et pariatur consequat. Excepteur ad ex fugiat est esse dolore consectetur ut ut dolor. Mollit consequat culpa laborum. aliquip sunt nostrud dolore consequat cillum labore. Dolor officia lorem do sunt nostrud aliqua velit voluptate.</p>
<p class="spacer"></p>
</div>

The following style sheet will make the div look like a little box and will allow the JavaScript to turn it into a marquee. The spacer p tags are also set here so that they are the same size as the div.

<style type="text/css">
#marquee_replacement{
 border:1px solid #000;
 width:200px;
 height:150px;
 overflow:auto;
}
#marquee_replacement p.spacer{
 height:150px;
}
</style>


Here is the JavaScript.

<script type="text/javascript">
// <!--
var speed = 5; // change scroll speed with this value
/**
 * Initialize the marquee, and start the marquee by calling the marquee function.
 */
function init(){
  var el = document.getElementById("marquee_replacement");
  el.style.overflow = 'hidden';
  scrollFromBottom();
}
 
var go = 0;
/**
 * This is where the scroll action happens.
 * Recursive method until stopped.
 */
function scrollFromBottom(){
  var el = document.getElementById("marquee_replacement");
  if(el.scrollTop >= el.scrollHeight-150){
    el.scrollTop = 0;
  };
  el.scrollTop = el.scrollTop + speed;
  if(go == 0){
    setTimeout("scrollFromBottom()",50);
  };
}
 
/**
 * Set the stop variable to be true (will stop the marquee at the next pass).
 */
function stop(){
  go = 1;
}
 
/**
 * Set the stop variable to be false and call the marquee function.
 */
function startit(){
  go = 0;
  scrollFromBottom();
}
// -->
</script>

You will also need to set an onload event on the body tag so that the init() function is run when the page loads. The init() function sets the overflow of the div to be hidden so that no scroll bar appears on it. This has to be done after the page has loaded as it doesn’t seem to do anything when set in the main style sheet. The init() function then calls the scrollFromBottom() function which just moves the text a littler higher up the page and then calls itself to repeat the process. Once the bottom of the text goes past the top of the div the height is reset and the process repeats.

You need a <p class="spacer"></p> at the start end end of the marquee. This creates a buffer zone which makes the marquee look more natural, but not only that the height of the elements is worked out with the spacer classes in mind. You also need to make sure that you give the spacer tags a specific height. For instance, in the code above I have set the height of the spacer tags to be 150px. You must then make sure that the scrollHeight of the marquee is subtracted by the height of a spacer tag. Take a look at line 12 of the JavaScript.

The div tag is also the given two events of on mouse out and on mouse over. These functions are in place to stop the text from scrolling when a user moves their mouse over it. This can be left out or kept in depending on what you want the marquee to do, but is replicates the original functionality of the HTML marquee.

Have a look at the example of vertical scrolling JavaScript marquee.

Horizontal Scrolling

Horizontal scrolling is slightly different. It uses the scrollLeft property of the main containing div but there is some initial set up needed to figure out how much scrolling is needed. In order to get the text inside the div to scroll you need to use a inner div, which contains a set of p tags, two of which are spacer tags. The inner div is used to keep the p tags in a single line. Here is the HTML code used to the horizontal scrolling marquee.

<div id="marquee_replacement" onmouseout="startit();" onmouseover="stop();">
<div id="start"><p class="spacer"></p>
<p>Lorem ipsum dolor sit amet consectetur enim proident in elit est. Culpa sit ad aliquip laboris sit ad tempor in dolore proident. Ut ut deserunt laboris ut exercitation sit consectetur nisi sunt incididunt. Nisi non et qui adipisicing labore tempor consequat anim id dolore. Veniam velit aliquip laborum. cillum dolor amet sed dolore laborum. in. Magna deserunt veniam anim ut deserunt est ut ut.</p>
<p>Aute enim quis duis exercitation magna cupidatat ullamco duis voluptate ullamco. Ad eu est in commodo occaecat mollit officia sit elit excepteur. Elit sint duis excepteur reprehenderit consequat cupidatat quis esse occaecat elit. Officia tempor laborum. dolore dolore nulla ea adipisicing pariatur irure deserunt. Enim ullamco mollit ut eu lorem elit ex sit cillum pariatur. Laboris laboris tempor ex ad officia eu.</p>
<p class="spacer"></p>
</div>
</div>

Next you will need to set some styles up in order to make the p tags appear in a line.

<style type="text/css">
#marquee_replacement{
 border:1px solid #000;
 width:1000px;
 height:20px;
 overflow:auto;
}
 
#marquee_replacement div#start p{
 padding:0;
 margin:0;
 left:0;
 width:auto;
 display:inline;
 float:left;
 white-space: nowrap;
 height:15px;
}
 
#marquee_replacement div#start p.spacer{
 width:1100px;
}
 
#marquee_replacement div#start{
 display:block;
 height:10px;
}
</style>


Finally here is the JavaScript needed. It works in the same way as the vertical scroller except that the required width of the inner div tag is worked out before the scrolling is started. The script takes all of the p tags in the inner div and totals how wide each of them is. The looping function then only has to go as far as that, minus the width of the marquee_replacement div.

<script type="text/javascript">
// <!--
var pWidth = 0;
var speed = 5; // change scroll speed with this value
/**
 * Get a collection of all of the objects of a particular type, can pass in an object that they should be collected from.
 */
function getElementsByTagNames(list,obj) {
  if (!obj) var obj = document;
  var tagNames = list.split(',');
  var resultArray = new Array();
  for (var i=0;i<tagNames.length;i++) {
    var tags = obj.getElementsByTagName(tagNames[i]);
    for (var j=0;j<tags.length;j++) {
      resultArray.push(tags[j]);
    };
  };
  var testNode = resultArray[0];
  if(!testNode){
    return [];
  };
  if(testNode.sourceIndex){
    resultArray.sort(function(a,b){
      return a.sourceIndex - b.sourceIndex;
    });
  }else if(testNode.compareDocumentPosition){
    resultArray.sort(function(a,b){
      return 3 - (a.compareDocumentPosition(b) & 6);
    });
  };
  return resultArray;
}
 
/**
 * Initialize the marquee, and start the marquee by calling the marquee function.
 */
function init(){
  var div = document.getElementById("marquee_replacement");
  div.style.overflow = 'hidden';
  
  var ps = getElementsByTagNames('p',div);
  for(var j=0;j<ps.length;j++){
    pWidth += ps[j].offsetWidth;
  }
 
  var startdiv = document.getElementById("start");
  startdiv.style.width = pWidth+'px';
  div.scrollLeft = 0;
  setTimeout("scrollFromBottom()",50);
}
 
var go = 0;
var timeout = '';
 
/**
 * This is where the scroll action happens.
 * Recursive method until stopped.
 */
function scrollFromSide(){
  var el = document.getElementById("marquee_replacement");
  if(el.scrollLeft >= pWidth-1000){
    el.scrollLeft = 0;
  };
  el.scrollLeft = el.scrollLeft+speed;
  if(go == 0){
    timeout = setTimeout("scrollFromSide()",50);
  };
}
 
/**
 * Set the stop variable to be true (will stop the marquee at the next pass).
 */
function stop(){
  go = 1;
  timeout = '';
}
 
/**
 * Set the stop variable to be false and call the marquee function.
 */
function startit(){
  go = 0;
  scrollFromSide();
}
// –>
</script>

Have a look at the example of horizontal scrolling JavaScript marquee.

Debugging

If you are stuck as to why the marquee isn’t working then you can do the following.

Add this line of HTML anywhere in your page, preferably near to where you have put the marquee.
<p id="test"></p>

Add the following line of JavaScript to your marquee script. You will want to put it just after the function declaration for scrollFromBottom() for vertical Scrolling and scrollFromSide() for horizontal scrolling.

document.getElementById('test').innerHTML = el.scrollTop+ ' ' +el.scrollHeight;

This should print out two numbers. The second will be the height of the marquee element and will remain constant. The first number will increase (or decrease if you have created a backwards scrolling marquee) as the scrolling takes place. The first number will be reset when it gets to the end of the marquee. If it doesn’t, or it gets to a certain value and stops then you need to look at the following line of code (from scrollFromBottom() in this case).

if(el.scrollTop >= el.scrollHeight-150){
 el.scrollTop = 0;
};

The value of 150 here needs to be the same as the height you set for the <p class="spacer"></p> tag in your CSS. If it is less than the value then it will never repeat itself. If it is greater than the value then it will repeat before it gets to the bottom.

Update

30/01/2007 - Added both vertical and horizontal scrolling.
22/05/2008 - Small bug noticed in the getElementsByTagNames() function due to a encoding typo. Also needed to start the marquee off in the init() function.
28/08/2008 - Added some helpful descriptions and comments.