show(), hide(), vanila Javascript

[Jolied]

without jquery show() and hide() example

   var obj = document.getElementById('add_show');
document.querySelector('#close_add').onclick = function() {
  obj.style.display = 'none';
};
document.querySelector('#add').onclick = function() {
  obj.style.display = 'block';
};

.button {
  display: inline-block;
  background: green;
  border-radius: 2px;
  color: white;
  padding: 7px 11px;
  font-size: 22px;
  cursor: pointer;
}
#add_show {
  position: absolute;
  top: 50px;
  left: 0;
  width: 200px;
  height: 200px;
  background: white;
  border: 1px solid black;
  display: none;
}
#close_add {
  font-size: 25px;
  color: #868686;
  font-weight: 400;
  position: absolute;
  top: 10px;
  left: 8px;
  transform: rotate(45deg);
}

<div class="button" id="add">Добавить
  <div id="add_show">
    <div id="close_add">+</div>
  </div>
</div>

[simrah]

 var obj = document.getElementById('add_show');
document.querySelector('#close_add').onclick = function(event) {
  event.stopPropagation();
  obj.style.display = 'none';
};
document.querySelector('#add').onclick = function() {
  obj.style.display = 'block';
};

.button {
  display: inline-block;
  background: green;
  border-radius: 2px;
  color: white;
  padding: 7px 11px;
  font-size: 22px;
  cursor: pointer;
}
#add_show {
  position: absolute;
  top: 50px;
  left: 0;
  width: 200px;
  height: 200px;
  background: white;
  border: 1px solid black;
  display: none;
}
#close_add {
  font-size: 25px;
  color: #868686;
  font-weight: 400;
  position: absolute;
  top: 10px;
  left: 8px;
  transform: rotate(45deg);
}

<div class="button" id="add">Добавить
  <div id="add_show">
    <div id="close_add">+</div>
  </div>
</div>