lib: eliminate mixMeta helper

Author: Qard

lib/metrics.js

@@ -43,19 +43,6 @@ const { performance } = require('perf_hooks');
 
 const newMetricChannel = channel('metrics:new');
 
-/**
- * Mix two metadata objects together.
- * @param {object} a The first metadata object.
- * @param {object} b The second metadata object.
- * @returns {object} The mixed metadata.
- * @private
- */
-function mixMeta(a, b) {
-  if (a === undefined) return b;
-  if (b === undefined) return a;
-  return ObjectAssign({}, a, b);
-}
-
 /**
  * Represents a single reported metric.
  */
@@ -221,7 +208,7 @@ class Metric {
     // Skip report construction if there are no subscribers.
     if (!this.shouldReport) return;
     const report = new MetricReport(this.type, this.name, value,
-                                    mixMeta(this.meta, meta));
+                                    ObjectAssign({}, this.meta, meta));
     this.#channel.publish(report);
   }
 }
@@ -352,7 +339,7 @@ class Timer extends Gauge {
    * @property {object} meta
    */
   get meta() {
-    return mixMeta(this.metric.meta, this.#meta);
+    return ObjectAssign({}, this.metric.meta, this.#meta);
   }
 
   /**
@@ -365,7 +352,7 @@ class Timer extends Gauge {
     if (!this.metric.shouldReport) return;
     this.end = performance.now();
     this.duration = this.end - this.start;
-    this.reset(this.duration, mixMeta(this.#meta, meta));
+    this.reset(this.duration, ObjectAssign({}, this.#meta, meta));
     return this.duration;
   }