Add FleBox itens

by Lucas Silva

HTML

<button id="add">Adicionar</button>

<div class="flex-container">
  <div class="flex-item">Item</div>
  <div class="flex-item">Item</div>
  <div class="flex-item">Item</div>
  <div class="flex-item">Item</div>
  <div class="flex-item">Item</div>
  <div class="flex-item">Item</div>
  <div class="flex-item">Item</div>
  <div class="flex-item">Item</div>
  <div class="flex-item">Item</div>
  <div class="flex-item">Item</div>
</div>

CSS

* {
  box-sizing: border-box;  
}

body {
  background: linear-gradient(135deg, #b04, #f80) fixed;
}
.flex-container {
  display: flex;
  flex-wrap: wrap;
}

.flex-item {
  flex-grow: 1;
  min-width: 25%;
  padding: 10px 0;
  background-color: rgba(255, 0, 0, 0.25);
  text-align: center;
  border: 1px solid rgba(255, 255, 255, 0.75);
  background-color: rgba(255, 255, 255, 0.2);
  color: rgba(255, 255, 255, 0.9);
  margin: 10px;
}

@media (max-width: 700px) {
  .flex-item {
    min-width: 33.333333%; 
  }
}

@media (max-width: 400px) {
  .flex-item {
    min-width: 50%; 
  }
}

JavaScript

document.getElementById('add').onclick = function(e){
  var gina = document.querySelector('.flex-container');
  var item = document.querySelector('.flex-item').cloneNode(true);
  gina.appendChild(item);
}