JSFiddle - React, Tailwind, and code Playground

HTML

<div id="navigation">
    <ul class="nav">
         <li class="main1"><a href="about.php">about us</a>
              <ul class="sub_menu" style="opacity:0">
                   <li><a href="1.html">1</a></li>
                   <li><a href="2.html">2</a></li>
              </ul>
         </li>
    </ul>
</div>

JavaScript

$(".main1 :contains(about us)").hover(function(){
     $(".main1 .sub_menu").css("opacity","1");
},function(){
$(".main1 .sub_menu").css("opacity","0");
});