W3Schools Tryit Editor

<!DOCTYPE html>
<html>
<head>
<style> 
#main {
  width: 400px;
  height: 150px;
  border: 1px solid #000000;
  display: flex;
}

#main div {
  width: 70px;
  height: 70px;
}
</style>
</head>
<body>

<h1>Change order with JavaScript</h1>

<p>Click the "Try it" button to change the order of the four DIV's:</p>

<p><b>Note:</b> Internet Explorer 10 and earlier versions do not support the order property.</p>

</body>

</html>