Script to defer CSS if non-critical to improve PageSpeed

defer-css.js

// List of css file(s) to be deferred
var deferred_css = [
  "example-1.css",
  "example-2.css",
];

function insertCss(value, index) {
  var link = document.createElement('link');
  link.rel = 'stylesheet';
  link.href = value;
  link.type = 'text/css';
  var existingLink = document.getElementsByTagName("link")[0];
  existingLink.parentNode.insertBefore(link, existingLink);
}

// loops through list and insert stylesheet to DOM
deferred_css.forEach(insertCss);