chore: remove let due to performance reasons

lib/customErrors.js

@@ -16,7 +16,7 @@ class AbortError extends RedisError {
     if (stack || stack === undefined) {
       Error.captureStackTrace(this, AbortError)
     }
-    for (let keys = Object.keys(obj), key = keys.pop(); key; key = keys.pop()) {
+    for (var keys = Object.keys(obj), key = keys.pop(); key; key = keys.pop()) {
       this[key] = obj[key]
     }
   }

lib/individualCommands.js

@@ -117,7 +117,7 @@ function infoCallback (self) {
     const lines = res.toString().split('\r\n')
     var line, parts, subParts
 
-    for (let i = 0; i < lines.length; i++) {
+    for (var i = 0; i < lines.length; i++) {
       parts = lines[i].split(':')
       if (parts[1]) {
         if (parts[0].indexOf('db') === 0) {

lib/multi.js

@@ -90,7 +90,7 @@ function execTransaction (multi) {
   // Silently ignore this error. We'll receive the error for the exec as well
   const promises = [multi._client.internalSendCommand(new Command('multi', [])).catch(() => {})]
   // Drain queue, callback will catch 'QUEUED' or error
-  for (let index = 0; index < len; index++) {
+  for (var index = 0; index < len; index++) {
     // The commands may not be shifted off, since they are needed in the result handler
     promises.push(pipelineTransactionCommand(multi, multi._queue.get(index), index).catch((e) => e))
   }
@@ -156,7 +156,7 @@ class Multi {
     // Either undefined or an array. Fail hard if it's not an array
     if (args) {
       // Legacy support for passing in an array of arguments
-      for (let i = 0; i < args.length; i++) {
+      for (var i = 0; i < args.length; i++) {
         const command = args[i][0]
         const tmpArgs = args[i].slice(1)
         if (Array.isArray(command)) {

lib/utils.js

@@ -62,7 +62,7 @@ function clone (obj) {
   var copy
   if (Array.isArray(obj)) {
     copy = new Array(obj.length)
-    for (let i = 0; i < obj.length; i++) {
+    for (var i = 0; i < obj.length; i++) {
       copy[i] = clone(obj[i])
     }
     return copy
@@ -70,7 +70,7 @@ function clone (obj) {
   if (Object.prototype.toString.call(obj) === '[object Object]') {
     copy = {}
     const elements = Object.keys(obj)
-    for (let elem = elements.pop(); elem !== undefined; elem = elements.pop()) {
+    for (var elem = elements.pop(); elem !== undefined; elem = elements.pop()) {
       copy[elem] = clone(obj[elem])
     }
     return copy