advanced String#stripTags() with whitelisting

gistfile1.js

String.prototype.stripTags = String.prototype.stripTags.wrap( 
  function(proceed, allowTags) { 
    if (allowTags) {
      if (Object.isString(allowTags)) allowTags = $w(allowTags)
      this.gsub(/(<\/?\s*)([^\s>]+)(\s[^>]*)?>/, function(match) {
        if (allowTags.include(match[2].toLowerCase()))
          return match[1] + match[2] + match[3] + '>'
      })
    } else {
      // proceed using the original function
      return proceed(); 
    }
  });