error message:
Unknown custom element: - did you register the component correctly? For recursive components, make sure to provide the "name" option.
modify
// error code
<script src="./lib/element-ui/element.js"></script>
<script src="./lib/vue.js"></script>
to
<script src="./lib/vue.js"></script>
<script src="./lib/element-ui/element.js"></script>