<nav>
  <ul>
    <li class="deroule"><a href="#">Ciquez<span class="fleche"></span></a>
      <ul>
        <li><a href="#">A propos</a></li>
        <li><a href="#">Services</a></li>
        <li><a href="#">Contact</a></li>
      </ul>
    </li>
    <li class="deroule"><a href="#">Ciquez<span class="fleche"></span></a>
      <ul>
        <li><a href="#">A propos</a></li>
        <li><a href="#">Services</a></li>
        <li><a href="#">Contact</a></li>
      </ul>
    </li>
    <li><a href="#">Contact</a></li>
  </ul>
</nav>
/* reset */
*{
  box-sizing: border-box;
}
ul{
  list-style-type: none;
  margin: 0;
  padding: 0;
}

/* custom menu */
nav:after{
  content: "";
  clear: both;
  display: block;
}
nav a{
  display: block;
  text-decoration: none;
  margin: 1px;
}
nav ul ul{
  background-color: #fff;
  display: none;
  position: absolute;
    width: 100%;
}
nav>ul>li{
  float: left;
  position: relative;
}
nav ul li a{
  background-color: silver;
  padding: 10px 20px;
  color: black;
  text-align: center;
}
nav>ul>li>a{
  background-color: rgb(50,50,60);;
  color: white;
} 
nav ul ul a:hover{
  background-color: black;
  color: silver;
}
.fleche {
    display: inline-block;
    width: 0;
    height: 0;
    margin-left: 4px;
    vertical-align: middle;
    border-top: 6px solid;
    border-right: 6px solid transparent;
    border-left: 6px solid transparent;
}


(function() {
  var tabMenu = document.querySelectorAll('.deroule');
  var tabD = document.querySelectorAll('ul ul');
  function deroule(e){
    e.stopPropagation(); 
    obj = this.querySelector('ul');
    if(!this.open){
      tabMenu.forEach(ferme);
      obj.style.display = "block";
      this.open = true;
    }else{
      obj.style.display = "none";
      this.open = false;
    }
  }
  var ferme = function(obj,i){
    tabD[i].style.display = "none";
    obj.open = false;
  }
  var init = function(obj){
    obj.addEventListener("click",deroule);
    obj.open = false;
  }
  tabMenu.forEach(init);
  window.addEventListener("click",function(){
    tabMenu.forEach(ferme);
  });
}).call(this);  
Rerun