lib: refactor internal/freelist

PR-URL: https://github.com/nodejs/node/pull/11406
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Michaël Zasso <targos@protonmail.com>

lib/internal/freelist.js

@@ -1,24 +1,25 @@
 'use strict';
 
-// This is a free list to avoid creating so many of the same object.
+class FreeList {
-exports.FreeList = function(name, max, constructor) {
+  constructor(name, max, ctor) {
     this.name = name;
-  this.constructor = constructor;
+    this.ctor = ctor;
     this.max = max;
     this.list = [];
-};
+  }
-
 
-exports.FreeList.prototype.alloc = function() {
+  alloc() {
     return this.list.length ? this.list.pop() :
-                            this.constructor.apply(this, arguments);
+                              this.ctor.apply(this, arguments);
-};
+  }
-
 
-exports.FreeList.prototype.free = function(obj) {
+  free(obj) {
     if (this.list.length < this.max) {
       this.list.push(obj);
       return true;
     }
     return false;
-};
+  }
+}
+
+module.exports = {FreeList};