include css via javascript code example

Example 1: javascript add css file

var cssFile = document.createElement('link');
    cssFile.rel = 'stylesheet';
    cssFile.href = "styles.css";  // or path for file {themes('/styles/mobile.css')}
    document.head.appendChild(cssFile); // append css to head element

Example 2: add css style sheet with javascript

<head>

<script>
function myFunction() {
  var x = document.createElement("LINK");
  x.setAttribute("rel", "stylesheet");
  x.setAttribute("type", "text/css");
  x.setAttribute("href", "styles.css");
  document.head.appendChild(x);
}
myFunction()
</script>

</head>