fix: skip .entries and Object.entries in for loop to improve flamegraph (elastic#2066)

Author: astorm

lib/tracecontext/tracestate.js

@@ -44,7 +44,8 @@ class TraceState {
     // values for our namespace, set via setValue to
     // ensure names conform
     this.values = {}
-    for (const [key, value] of Object.entries(defaultValues)) {
+    for (const key in defaultValues) {
+      const value = defaultValues[key]
       this.setValue(key, value)
     }
   }
@@ -213,7 +214,8 @@ class TraceState {
   toW3cString () {
     const json = this.toObject()
     const chars = []
-    for (const [key, value] of Object.entries(json)) {
+    for (const key in json) {
+      const value = json[key]
       if (!value) { continue }
       chars.push(key)
       chars.push('=')
@@ -226,7 +228,8 @@ class TraceState {
 
   _serializeValues (keyValues) {
     const chars = []
-    for (const [key, value] of Object.entries(keyValues)) {
+    for (const key in keyValues) {
+      const value = keyValues[key]
       chars.push(`${key}:${value}`)
       chars.push(';')
     }
@@ -272,7 +275,7 @@ class TraceState {
     const bytes = []
 
     const parts = string.split(',')
-    for (const [, part] of parts.entries()) {
+    for (const part of parts) {
       if (!part) { continue }
       const [listMember, value] = part.split('=')
       if (!listMember || !value) { continue }
@@ -292,7 +295,8 @@ class TraceState {
 
   static _parseValues (rawValues) {
     const parsedValues = {}
-    for (const [, keyValue] of rawValues.split(';').entries()) {
+    const parts = rawValues.split(';')
+    for (const keyValue of parts) {
       if (!keyValue) { continue }
       const [key, value] = keyValue.split(':')
       if (!key || !value) { continue }
@@ -324,8 +328,8 @@ class TraceState {
         if (key === listMemberNamespace) {
           const rawValues = buffer.slice(indexOfValue, indexOfValue + lengthValue).toString()
           const parsedValues = TraceState._parseValues(rawValues)
-          for (const [key, value] of Object.entries(parsedValues)) {
-            values[key] = value
+          for (const key in parsedValues) {
+            values[key] = parsedValues[key]
           }
           continue
         } else {