How to add alpha filter to any HTML element and keep the other filters in IE?

Question

If I have this HTML

Then this javascript works in IE6

Answer 1

After some more testing, I come with this solution

var filter = function(obj,f,params) {
  var found, nf, dx = "DXImageTransform.Microsoft.";

  // check if DXImageTransform.Microsoft.[Filter] or [Filter] filter is set
  try { nf = obj.filters.item(dx+f); found = true; } catch(e) {}
  if(!found) try { nf = obj.filters.item(f); found = true; } catch(e) {}

  // filter is set - change existing one
  if(found) {
    nf.Enabled = true; // if exists, it might be disabled
    if(params) for(var i in params) nf[i] = params[i];
  }

  // filter is not set - apply new one
  else {
    nf = "";
    if(params) for(var i in params) nf+= i.toLowerCase()+"="+params[i]+",";
    if(params) nf = "("+nf.substr(0,nf.length-1)+")";
    obj.style.filter+= "progid:"+dx+f+nf+" ";
  }

  // hasLayout property hack
  if(!obj.style.zoom) obj.style.zoom = 1;
};

Example

var obj = document.getElementById("a");
if(document.body.filters) filter(obj,"Alpha",{Opacity:50});

I hope this works, if anybody finds a problem, please tell me.

Sources

obj.filters property http://msdn.microsoft.com/en-us/library/ms537452(VS.85).aspx

filter.Alpha http://msdn.microsoft.com/en-us/library/ms532967(VS.85).aspx