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ParentNode.childElementCount

The ParentNode.childElementCount read-only property returns an unsigned long representing the number of child elements of the given element.

This property was initially defined in the ElementTraversal pure interface. As this interface contained two distinct set of properties, one aimed at Node that have children, one at those that are children, they have been moved into two separate pure interfaces, ParentNode and ChildNode. In this case, childElementCount moved to ParentNode. This is a fairly technical change that shouldn't affect compatibility.

Syntax

var elCount = elementNodeReference.childElementCount;

Polyfill for Internet Explorer 8

This property is unsupported prior to IE9, so the following snippet can be used to add support to IE8:

// Source: https://github.com/Alhadis/Snippets/blob/master/js/polyfills/IE8-child-elements.js
if(!("childElementCount" in document.documentElement)){
    Object.defineProperty(Element.prototype, "childElementCount", {
        get: function(){
            for(var c = 0, nodes = this.children, n, i = 0, l = nodes.length; i < l; ++i)
                (n = nodes[i], 1 === n.nodeType) && ++c;
            return c;
        }
    });
}

Polyfill for Internet Explorer 9+ and Safari

// Source: https://github.com/jserz/js_piece/blob/master/DOM/ParentNode/childElementCount/childElementCount.md
(function (arr) {
  arr.forEach(function (item) {
    if (item.hasOwnProperty('childElementCount')) {
      return;
    }
    Object.defineProperty(item, 'childElementCount', {
      configurable: true,
      enumerable: true,
      get: function () {
        var el = this.firstChild,
          count = 0;
        while (el) {
          if (el.nodeType === 1) {
            ++count;
          }
          el = el.nextSibling
        }
        return count;
      },
      set: undefined
    });
  });
})([Element.prototype, Document.prototype, DocumentFragment.prototype]);

Specification

Specification	Status	Comment
DOM The definition of 'ParentNode.childElementCount' in that specification.	Living Standard	Split the `ElementTraversal` interface in `ChildNode` and `ParentNode`. This method is now defined on the latter. The `Document` and `DocumentFragment` implemented the new interfaces.
Element Traversal Specification The definition of 'ElementTraversal.childElementCount' in that specification.	Recommendation	Added its initial definition to the `ElementTraversal` pure interface and use it on `Element`.

Browser compatibility

Feature	Chrome	Firefox (Gecko)	Internet Explorer	Opera	Safari
Basic support (on `Element`)	1.0	3.5 (1.9.1)	9.0	10.0	4.0
Support on `Document` and `DocumentFragment`	29.0	25.0 (25.0)	No support	16.0	No support