code: function indexOfNode (host, node) {
    const chs = host.childNodes;
    const chsLen = chs.length;
    for (let a = 0; a < chsLen; a++) {
      if (chs[a] === node) {
        return a;
      }
    }
    return -1;
  }
docs: Returns the index of the node in the host's childNodes.