Load CSS Stylesheet if it's not loaded already. This is incredibly helpful to include in your JS modules, right above the class, as a way of importing the CSS file for the module without having to track it all in the main html page.

load-stylesheet-if-not-loaded.js

function loadCSSSheetIfNotLoaded({url}){
  //Get the current stylesheets
  const currentStyles = Object.values(document.styleSheets);
  const foundSheet = currentStyles.find(sheet => sheet.href ? sheet.href.indexOf(url) != -1 : false);
  if(!foundSheet){
    //Didn't find the stylesheet, so let's add it
    $(`<link href="${url}" rel="stylesheet">`).appendTo("head");
  }
}