javascript - Is it possible to get element's numerical index in its parent node without looping?

Question

Normally I'm doing it this way:

for(i=0;i<elem.parentNode.length;i++) {
  if (elem.parentNode[i] == elem) //.... etc.. etc...
}

Answer 1

function getChildIndex(node) {
  return Array.prototype.indexOf.call(node.parentNode.childNodes, node);
}

This seems to work in Opera 11, Firefox 4, Chromium 10. Other browsers untested. It will throw TypeError if node has no parent (add a check for node.parentNode !== undefined if you care about that case).

Of course, Array.prototype.indexOf does still loop, just within the function call. It's impossible to do this without looping.

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Note: If you want to obtain the index of a child Element, you can modify the function above by changing childNodes to children.

function getChildElementIndex(node) {
  return Array.prototype.indexOf.call(node.parentNode.children, node);
}