JSFiddle - React, Tailwind, and code Playground

HTML

<a href="" id="lien">
 afficher
 </a>
 <div class="div_flag">

</div>

CSS

html, body {
  height: 100%;
  }

.div_flag {
  width: 100px;
  height: 100px;
  background-color: red;
}

JavaScript

$(function(){

function showFlags() {
    $(".div_flag").show();
}

$('#lien').on('click',function(e){ e.stopPropagation();e.preventDefault();showFlags()})

$('body').not('#lien').click(function() {
    if ($(".div_flag").is(":visible")) {
        alert("visible");
 $(".div_flag").hide()
 
    } else {
        alert("visible NON");
        showflags();
    }
 
});

})