Demo: CSS margin-right

<div class='container'>
  <div class='box'>Box 1</div>
  <div class='box'>Box 2</div>
</div>

.container {
  display: flex;
}

.box {
  background-color: lightblue;
  padding: 20px;
  margin-right: 20px;
  border: 1px solid blue;
}

.box:last-child {
  margin-right: 0;
}

// No JavaScript required for this demo