executeOnDomNodeLoaded polls the DOM repeatedly until the DOM node is in the DOM, and then executes the callback

executeOnDomNodeLoaded.js

function executeOnDomNodeLoaded(node, func) {
   // This function will check, every tenth of a second, to see if 
   // our element is a part of the DOM tree - as soon as we know 
   // that it is, we execute the provided function.
   var findUltimateAncestor = function(node) {
         // Walk up the DOM tree until we are at the top (parentNode 
         // will return null at that point).
         // NOTE: this will return the same node that was passed in 
         // if it has no ancestors.
         var ancestor = node;
         while(ancestor.parentNode) {
            ancestor = ancestor.parentNode;
         }
         return ancestor;
      },
      isInDOMTree = function(node) {
         // If the farthest-back ancestor of our node has a "body"
         // property (that node would be the document itself), 
         // we assume it is in the page's DOM tree.
         return !!(findUltimateAncestor(node).body);
      };

   if(isInDOMTree(node)) {
      func();
   } else {
      setTimeout(function() { executeOnDomNodeLoaded(node, func); }, 100);
   }
}