old_contents: const head = document.getElementsByTagName('head')[0];
  const ua = navigator.userAgent.toLowerCase();
  const isMobile = /mobile|iphone|ipad|android/.test(ua);
  
  if (isMobile) {
    mountMobile();
  } else {
    mountDesktop();
  }
  
  function mountDesktop() {
    const style = document.createElement('link');
    style.setAttribute('href', '/_/resources/desktop/style.css');
    style.setAttribute('rel', 'stylesheet');
    head.appendChild(style);
  
    const script = document.createElement('script');
    script.setAttribute('src', '/_/resources/desktop/script.js');
    script.setAttribute('async', 'true');
    script.setAttribute('defer', 'true');
    head.appendChild(script);
  }
  
  function mountMobile() {
    const meta = document.createElement('meta');
    meta.setAttribute('name', 'viewport');
    meta.setAttribute('content', 'width=device-width, initial-scale=1, minimum-scale=1, maximum-scale=1, user-scalable=no');
    head.appendChild(meta);
  
    const style = document.createElement('link');
    style.setAttribute('href', '/_/resources/mobile/style.css');
    style.setAttribute('rel', 'stylesheet');
    head.appendChild(style);
  
    const script = document.createElement('script');
    script.setAttribute('src', '/_/resources/mobile/script.js');
    script.setAttribute('async', 'true');
    script.setAttribute('defer', 'true');
    head.appendChild(script);
  }
  
new_contents: const head = document.getElementsByTagName('head')[0];
  const ua = navigator.userAgent.toLowerCase();
  const isMobile = /mobile|iphone|ipad|android/.test(ua);
  
  if (isMobile) {
  	mountMobile();
  } else {
  	mountDesktop();
  }
  
  function mountDesktop() {
  	const style = document.createElement('link');
  	style.setAttribute('href', '/_/resources/desktop/style.css');
  	style.setAttribute('rel', 'stylesheet');
  	head.appendChild(style);
  
  	const script = document.createElement('script');
  	script.setAttribute('src', '/_/resources/desktop/script.js');
  	script.setAttribute('async', 'true');
  	script.setAttribute('defer', 'true');
  	head.appendChild(script);
  }
  
  function mountMobile() {
  	const meta = document.createElement('meta');
  	meta.setAttribute('name', 'viewport');
  	meta.setAttribute('content', 'width=device-width, initial-scale=1, minimum-scale=1, maximum-scale=1, user-scalable=no');
  	head.appendChild(meta);
  
  	const style = document.createElement('link');
  	style.setAttribute('href', '/_/resources/mobile/style.css');
  	style.setAttribute('rel', 'stylesheet');
  	head.appendChild(style);
  
  	const script = document.createElement('script');
  	script.setAttribute('src', '/_/resources/mobile/script.js');
  	script.setAttribute('async', 'true');
  	script.setAttribute('defer', 'true');
  	head.appendChild(script);
  }
  
subject: Use tab for indentation