http://stackoverflow.com/a/28210364/1070244
判断自定义元素，是否为未知元素
chrome和firefox存在差异，尤老 研究的代码
// Chrome returns unknown for several HTML5 elements.
// https://code.google.com/p/chromium/issues/detail?id=540526
// Firefox returns unknown for some "Interactive elements."
原文：https://www.cnblogs.com/leee/p/9031463.html