Cut off IIS virtual path (base url) from the request url when running with IISNODE

iisnode-baseurl.js

// Cut off IIS virtual path (base url) from the request url when running via IISNODE
// with URL Rewrite
//
// Add "APPL_MD_PATH" to "promoteServerVars" iisnode attribute in web.config
var iisNodeBaseUrl = function () {
	return function (req, res, next) {
		var appMdPath = req.headers['x-iisnode-appl_md_path'];

		if (appMdPath) {			
			var rootPos = appMdPath.search("/ROOT");
			if (rootPos > -1) {
				// e.g. '/LM/W3SVC/1/ROOT/testbaseurl' -> '/testbaseurl'
				var baseUrl = appMdPath.slice(appMdPath.search("/ROOT") + ("/ROOT").length);
				if (baseUrl <> "") {
					// e.g. '/testbaseurl/assets/js/script.js' -> '/assets/js/script.js'
					req.url = req.url.replace(baseUrl, "");		
				}				
			}			
		}

		return next();
	};
};

web.config.sample.xml

<configuration>
	<system.webServer>
		<handlers>
			<add name="iisnode" path="index.js" verb="*" modules="iisnode" />
		</handlers>    
		
		<iisnode promoteServerVars="APPL_MD_PATH" />
		
		<rewrite>
			<rules>
				<rule name="server">
					<match url="/*" />
					<action type="Rewrite" url="index.js" />
				</rule>
			</rules>
		</rewrite>
	</system.webServer>
</configuration>