JavaScript ElementTraversal proposal

27 July W3 announced a new Working Draft, called: ElementTraversal

This is a "new" feature but today it's not cross browser so this is my proposal to have Element Trasversal with every recent browser:

(ElementTraversal = function(node){
 this.node = node;
 this.firstElementChild = this.getFirstElementChild();
 this.lastElementChild = this.getLastElementChild();
 this.previousElementSibling = this.getPreviousElementSibling();
 this.nextElementSibling = this.getNextElementSibling();
 this.childElementCount = this.getChildElementCount();
 
}).extend(null, {
 getFirstElementChild:function(){
  for(var c = this.node.childNodes,
   i = 0,
   j = (c && c.length) || 0,
   e;
   i < j;
   i++
  ){
   if(c[i].nodeType === 1)
    e = c[j = i];
  };
  return e;
 },
 getLastElementChild:function(){
  for(var c = this.node.childNodes,
   i = ((c && c.length) || 0) - 1,
   j = -1,
   e;
   i > j;
   i--
  ){
   if(c[i].nodeType === 1)
    e = c[j = i];
  };
  return e;
 },
 getPreviousElementSibling:function(){
  var e = this.node.previousSibling;
  while(e && e.nodeType !== 1)
   e = e.previousSibling;
  return e;
 },
 getNextElementSibling:function(){
  var e = this.node.nextSibling;
  while(e && e.nodeType !== 1)
   e = e.nextSibling;
  return e;
 },
 getChildElementCount:function(){
  for(var c = this.node.childNodes,
   i = 0,
   j = (c && c.length) || 0,
   n = 0;
   i < j;
   i++
  ){
   if(c[i].nodeType === 1)
    ++n;
  };
  return n;
 },
 update:function(){
  this.constructor.call(this, this.node);
  return this;
 }
});

And this is a basic test:

test

 
test
 test
 test

test

My proposal is based on extend Function prototype, You can find them here.

Just a note about update extra method: not every browser support a defineGetter / setter method so update is a quick way to have correct properties.

If You create an instance and You modify some node, You should use:

ET.update();

This method returns instance itself, so You can pass them directly on other functions.