code: function renderSimpleRuby( $ruby ) {
    var frag = $.create( '!' )
    var clazz = $ruby.classList
    var $rb, $ru
  
    frag.appendChild( $.clone( $ruby ))
  
    $
    .tag( 'rt', frag.firstChild )
    .forEach(function( $rt ) {
      var $rb = $.create( '!' )
      var airb = []
      var irb
  
      // Consider the previous nodes the implied
      // ruby base
      do {
        irb = ( irb || $rt ).previousSibling
        if ( !irb || irb.nodeName.match( /((?:h\-)?r[ubt])/i ))  break
  
        $rb.insertBefore( $.clone( irb ), $rb.firstChild )
        airb.push( irb )
      } while ( !irb.nodeName.match( /((?:h\-)?r[ubt])/i ))
  
      // Create a real `<h-ru>` to append.
      $ru = clazz.contains( 'zhuyin' ) ? createZhuyinRu( $rb, $rt ) : createNormalRu( $rb, $rt )
  
      // Replace the ruby text with the new `<h-ru>`,
      // and remove the original implied ruby base(s)
      try {
        $rt.parentNode.replaceChild( $ru, $rt )
        airb.map( $.remove )
      } catch ( e ) {}
    })
    return createCustomRuby( frag )
  }
docs: 1. Simple ruby polyfill; 2. Inter-character polyfill for Zhuyin