fix(loader): skip calculations

index.js

@@ -368,14 +368,14 @@ ExtractTextPlugin.prototype.apply = function(compiler) {
 				var asset = compilation.assets[name];
 
 				if (/\.js$/.test(name) && asset._source) {
-					var newName = name.replace(/\.js/, '.no_css.js');
-					var newAsset = new CachedSource(asset._source);
 					var regex = /\/\*__START_CSS__\*\/[\s\S]*?\/\*__END_CSS__\*\//g
 					var source = asset.source();
 
 					if (!source.match(regex)) {
 						return;
 					}
+					var newName = name.replace(/\.js/, '.no_css.js');
+					var newAsset = new CachedSource(asset._source);
 					// remove js that adds css to DOM via style-loader, so that React Loadable
 					// can serve smaller files (without css) in initial request.
 					newAsset._cachedSource = source.replace(regex, '');