perf: skip null-context bind in eachMapping; direct names array read

lib/source-map-consumer.js

@@ -173,8 +173,14 @@ SourceMapConsumer.prototype.eachMapping =
       throw new Error("Unknown order of iteration.");
     }
 
-    var boundCallback = aCallback.bind(context);
-    var names = this._names;
+    // Skip the `Function.prototype.bind` allocation when no context was
+    // supplied — `aCallback || null` defaults to a null context, which is
+    // the same as calling the function unbound.
+    var cb = context !== null ? aCallback.bind(context) : aCallback;
+    // Direct reads of the underlying `_array` slot match the slab-direct
+    // pattern in `_serializeMappings` / `fromSourceMap`. Skips the `at()`
+    // bounds-check + function call per named mapping.
+    var nameArray = this._names._array;
     // `_absoluteSources` is precomputed in both consumer constructors as
     // `computeSourceURL(sourceRoot, _sources.at(i), sourceMapURL)`, so a
     // direct index skips the per-call URL parse + resolve. Same memoization
@@ -183,13 +189,15 @@ SourceMapConsumer.prototype.eachMapping =
 
     for (var i = 0, n = mappings.length; i < n; i++) {
       var mapping = mappings[i];
-      boundCallback({
-        source: mapping.source === null ? null : absoluteSources[mapping.source],
+      var src = mapping.source;
+      var nm = mapping.name;
+      cb({
+        source: src === null ? null : absoluteSources[src],
         generatedLine: mapping.generatedLine,
         generatedColumn: mapping.generatedColumn,
         originalLine: mapping.originalLine,
         originalColumn: mapping.originalColumn,
-        name: mapping.name === null ? null : names.at(mapping.name)
+        name: nm === null ? null : nameArray[nm]
       });
     }
   };