fix usage of ES5 features

lib/Server.js

@@ -52,11 +52,11 @@ function Server(compiler, options) {
 	// Init express server
 	var app = this.app = new express();
 
-	app.all("*", (req, res, next) => {
+	app.all("*", function(req, res, next) {
 		if(this.checkHost(req.headers))
 			return next();
 		res.send("Invalid Host header");
-	});
+	}.bind(this));
 
 	// middleware for serving webpack bundle
 	this.middleware = webpackDevMiddleware(compiler, options);
@@ -333,10 +333,10 @@ Server.prototype.checkHost = function(headers) {
 
 	// get the Host header and extract hostname
 	// we don't care about port not matching
-	const hostHeader = headers.host;
+	var hostHeader = headers.host;
 	if(!hostHeader) return false;
-	const idx = hostHeader.indexOf(":");
-	const hostname = idx >= 0 ? hostHeader.substr(0, idx) : hostHeader;
+	var idx = hostHeader.indexOf(":");
+	var hostname = idx >= 0 ? hostHeader.substr(0, idx) : hostHeader;
 
 	// always allow localhost host, for convience
 	if(hostname === "127.0.0.1" || hostname === "localhost") return true;
@@ -346,8 +346,8 @@ Server.prototype.checkHost = function(headers) {
 
 	// also allow public hostname if provided
 	if(typeof this.publicHost === "string") {
-		const idxPublic = this.publicHost.indexOf(":");
-		const publicHostname = idxPublic >= 0 ? this.publicHost.substr(0, idx) : this.publicHost;
+		var idxPublic = this.publicHost.indexOf(":");
+		var publicHostname = idxPublic >= 0 ? this.publicHost.substr(0, idx) : this.publicHost;
 		if(hostname === publicHostname) return true;
 	}