code: function youtube(str) {
  	// shortcode
  	var shortcode = /youtube:\/\/|https?:\/\/youtu\.be\//g;
  
  	if (shortcode.test(str)) {
  		var shortcodeid = str.split(shortcode)[1];
  		return stripParameters(shortcodeid);
  	}
  
  	// /v/ or /vi/
  	var inlinev = /\/v\/|\/vi\//g;
  
  	if (inlinev.test(str)) {
  		var inlineid = str.split(inlinev)[1];
  		return stripParameters(inlineid);
  	}
  
  	// v= or vi=
  	var parameterv = /v=|vi=/g;
  
  	if (parameterv.test(str)) {
  		var arr = str.split(parameterv);
  		return arr[1].split('&')[0];
  	}
  
  	// v= or vi=
  	var parameterwebp = /\/an_webp\//g;
  
  	if (parameterwebp.test(str)) {
  		var webp = str.split(parameterwebp)[1];
  		return stripParameters(webp);
  	}
  
  	// embed
  	var embedreg = /\/embed\//g;
  
  	if (embedreg.test(str)) {
  		var embedid = str.split(embedreg)[1];
  		return stripParameters(embedid);
  	}
  
  	// user
  	var userreg = /\/user\/(?!.*videos)/g;
  
  	if (userreg.test(str)) {
  		var elements = str.split('/');
  		return stripParameters(elements.pop());
  	}
  
  	// attribution_link
  	var attrreg = /\/attribution_link\?.*v%3D([^%&]*)(%26|&|$)/;
  
  	if (attrreg.test(str)) {
  		return str.match(attrreg)[1];
  	}
  }
docs: Get the Youtube Video id.
  @param {string} str - the url from which you want to extract the id
  @returns {string|undefined}