optimize array operation

Author: sokra

lib/ChunkGraph.js

@@ -198,8 +198,11 @@ class ChunkGraph {
 			findGraphRoots(set, module => {
 				return moduleGraph
 					.getOutgoingConnections(module)
-					.map(connection => connection.module)
-					.filter(Boolean);
+					.reduce((arr, connection) => {
+						const module = connection.module;
+						if (module) arr.push(module);
+						return arr;
+					}, []);
 			})
 		).sort(compareModulesByIdentifier);
 	}