转js contains 方法

function Jcontains(root, el) {
    if (root.compareDocumentPosition)
        return root === el || !!(root.compareDocumentPosition(el) & 16);
        if (root.contains && el.nodeType === 1){
            return root.contains(el) && root !== el;
    }
    while ((el = el.parentNode))
    if (el === root) return true;
    return false;
}