ParentNode.children

Node.children 唯讀屬性會回傳一個 Node 之子元素的動態（live）HTMLCollection。

var children = node.children;

children 是一個 HTMLCollection，為一個有順序性、由 node 中的 DOM 子元素所組成的集合。假如沒有子元素，則 children 內便不包含任何元素，且 length 為 0。

var foo = document.getElementById('foo');
for (var i = 0; i < foo.children.length; i++) {
    console.log(foo.children[i].tagName);
}

// Overwrites native 'children' prototype.
// Adds Document & DocumentFragment support for IE9 & Safari.
// Returns array instead of HTMLCollection.
;(function(constructor) {
    if (constructor &&
        constructor.prototype &&
        constructor.prototype.children == null) {
        Object.defineProperty(constructor.prototype, 'children', {
            get: function() {
                var i = 0, node, nodes = this.childNodes, children = [];
                while (node = nodes[i++]) {
                    if (node.nodeType === 1) {
                        children.push(node);
                    }
                }
                return children;
            }
        });
    }
})(window.Node || window.Element);

[1] Internet Explorer 6, 7 and 8 supported it, but erroneously includes Comment (en-US) nodes.

• The ParentNode and ChildNode interfaces.
• Object types implementing this interface: Document, Element, and DocumentFragment.