lib: improve debuglog() performance

PR-URL: https://github.com/nodejs/node/pull/32260
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 14 insertions, 11 deletions

diff --git a/lib/internal/util/debuglog.js b/lib/internal/util/debuglog.js
index 72eb797474a..fce2e2f0d8c 100644
--- a/lib/internal/util/debuglog.js
+++ b/lib/internal/util/debuglog.js
@@ -35,6 +35,8 @@ function emitWarningIfNeeded(set) {
   }
 }
 
+function noop() {}
+
 function debuglogImpl(set) {
   set = set.toUpperCase();
   if (debugs[set] === undefined) {
@@ -48,7 +50,7 @@ function debuglogImpl(set) {
         process.stderr.write(format('%s %s: %s\n', set, coloredPID, msg));
       };
     } else {
-      debugs[set] = null;
+      debugs[set] = noop;
     }
   }
   return debugs[set];
@@ -58,16 +60,17 @@ function debuglogImpl(set) {
 // so it needs to be called lazily in top scopes of internal modules
 // that may be loaded before these run time states are allowed to
 // be accessed.
-function debuglog(set) {
-  let debug;
-  return function(...args) {
-    if (debug === undefined) {
-      // Only invokes debuglogImpl() when the debug function is
-      // called for the first time.
-      debug = debuglogImpl(set);
-    }
-    if (debug !== null)
-      debug(...args);
+function debuglog(set, cb) {
+  let debug = (...args) => {
+    // Only invokes debuglogImpl() when the debug function is
+    // called for the first time.
+    debug = debuglogImpl(set);
+    if (typeof cb === 'function')
+      cb(debug);
+    debug(...args);
+  };
+  return (...args) => {
+    debug(...args);
   };
 }