Javascript Snippet : Select All, None, Invert checkbox

//int mode
// mode = 0 invert selection
// mode = 1 select none
// mode = other than 0 or 1, select all
function checkChange(mode)
{
            for(i=0;i<document.forms[0].elements.length;i++)
            {
                var ele = document.forms[0].elements[i];
                if(ele.type == 'checkbox')
                {
                  if(ele.disabled=false)
                  {
                   if(mode==0) //invert selection
                        ele.checked = !ele.checked;
                   else if(mode==1) //none
                        ele.checked = false;
                   else
                        ele.checked = true;
                  }
                }
            }
}