Merge pull request #260 from MagicDuck/array_set_perf

using native javascript Map in array-set to improve memory usage

Author: tromey

lib/array-set.js

@@ -7,6 +7,7 @@
 
 var util = require('./util');
 var has = Object.prototype.hasOwnProperty;
+var hasNativeMap = typeof Map !== "undefined";
 
 /**
  * A data structure which is a combination of an array and a set. Adding a new
@@ -16,7 +17,7 @@ var has = Object.prototype.hasOwnProperty;
  */
 function ArraySet() {
   this._array = [];
-  this._set = Object.create(null);
+  this._set = hasNativeMap ? new Map() : Object.create(null);
 }
 
 /**
@@ -37,7 +38,7 @@ ArraySet.fromArray = function ArraySet_fromArray(aArray, aAllowDuplicates) {
  * @returns Number
  */
 ArraySet.prototype.size = function ArraySet_size() {
-  return Object.getOwnPropertyNames(this._set).length;
+  return hasNativeMap ? this._set.size : Object.getOwnPropertyNames(this._set).length;
 };
 
 /**
@@ -46,14 +47,18 @@ ArraySet.prototype.size = function ArraySet_size() {
  * @param String aStr
  */
 ArraySet.prototype.add = function ArraySet_add(aStr, aAllowDuplicates) {
-  var sStr = util.toSetString(aStr);
-  var isDuplicate = has.call(this._set, sStr);
+  var sStr = hasNativeMap ? aStr : util.toSetString(aStr);
+  var isDuplicate = hasNativeMap ? this.has(aStr) : has.call(this._set, sStr);
   var idx = this._array.length;
   if (!isDuplicate || aAllowDuplicates) {
     this._array.push(aStr);
   }
   if (!isDuplicate) {
-    this._set[sStr] = idx;
+    if (hasNativeMap) {
+      this._set.set(aStr, idx);
+    } else {
+      this._set[sStr] = idx;
+    }
   }
 };
 
@@ -63,8 +68,12 @@ ArraySet.prototype.add = function ArraySet_add(aStr, aAllowDuplicates) {
  * @param String aStr
  */
 ArraySet.prototype.has = function ArraySet_has(aStr) {
-  var sStr = util.toSetString(aStr);
-  return has.call(this._set, sStr);
+  if (hasNativeMap) {
+    return this._set.has(aStr);
+  } else {
+    var sStr = util.toSetString(aStr);
+    return has.call(this._set, sStr);
+  }
 };
 
 /**
@@ -73,10 +82,18 @@ ArraySet.prototype.has = function ArraySet_has(aStr) {
  * @param String aStr
  */
 ArraySet.prototype.indexOf = function ArraySet_indexOf(aStr) {
-  var sStr = util.toSetString(aStr);
-  if (has.call(this._set, sStr)) {
-    return this._set[sStr];
+  if (hasNativeMap) {
+    var idx = this._set.get(aStr);
+    if (idx >= 0) {
+        return idx;
+    }
+  } else {
+    var sStr = util.toSetString(aStr);
+    if (has.call(this._set, sStr)) {
+      return this._set[sStr];
+    }
   }
+
   throw new Error('"' + aStr + '" is not in the set.');
 };