util: refactor debuglog() from array regex to regex string

Author: TylerYang

lib/util.js

@@ -230,28 +230,21 @@ function format(f) {
   return str;
 }
 
-var debugs = {};
-var debugEnviron;
-
-const regExpSpecialChars = /[|\\{}()[\]^$+?.]/g;
-
-function stringToRegExp(string) {
-  // Escape special chars except wildcard.
-  string = string.replace(regExpSpecialChars, '\\$&');
-  // Transform wildcard to "match anything"
-  string = string.replace(/\*/g, '.*');
-  return new RegExp(`^${string}$`);
+const debugs = {};
+let debugEnvRegex = /^$/;
+if (process.env.NODE_DEBUG) {
+  let debugEnv = process.env.NODE_DEBUG;
+  debugEnv = debugEnv.replace(/[|\\{}()[\]^$+?.]/g, '\\$&')
+      .replace(/\*/g, '.*')
+      .replace(/,/g, '$|^')
+      .toUpperCase();
+  debugEnvRegex = new RegExp(`^${debugEnv}$`, 'i');
 }
 
 function debuglog(set) {
-  if (debugEnviron === undefined) {
-    debugEnviron = Array.from(new Set(
-      (process.env.NODE_DEBUG || '').split(',').map((s) => s.toUpperCase())));
-    debugEnviron = debugEnviron.map(stringToRegExp);
-  }
   set = set.toUpperCase();
   if (!debugs[set]) {
-    if (debugEnviron.some((name) => name.test(set))) {
+    if (debugEnvRegex.test(set)) {
       var pid = process.pid;
       debugs[set] = function() {
         var msg = exports.format.apply(exports, arguments);