如何用原生js截取所有li的文本内容并代替原本的内容

Question

比如

 <ul>

    <li>aaaaaaaaaaaaaaaaa</li>

    <li>aaaaaaaaaaaaaaaaa</li>

    <li>aaaaaaaaaaaaaaaaa</li>

    <li>aaaaaaaaaaaaaaaaa</li>

    <li>aaaaaaaaaaaaaaaaa</li>

 </ul>

 如果li的长度大于5 则显示

 <ul>

    <li>aaaaa...</li>

    <li>aaaaa...</li>

    <li>aaaaa...</li>

    <li>aaaaa...</li>

    <li>aaaaa...</li>

 </ul>