1 files changed, 11 insertions, 13 deletions

diff --git a/lib/scope.js b/lib/scope.js
index 40237b39..acc6fa25 100644
--- a/lib/scope.js
+++ b/lib/scope.js
@@ -75,7 +75,7 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(){
     // pass 1: setup scope chaining and handle definitions
     var self = this;
     var scope = self.parent_scope = null;
-    var labels = {};
+    var labels = Object.create(null);
     var tw = new TreeWalker(function(node, descend){
         if (node instanceof AST_Scope) {
             node.init_scope_vars();
@@ -157,7 +157,7 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(){
 
     // pass 2: find back references and eval
     var func = null;
-    var globals = self.globals = {};
+    var globals = self.globals = Object.create(null);
     var tw = new TreeWalker(function(node, descend){
         if (node instanceof AST_Lambda) {
             var prev_func = func;
@@ -175,7 +175,7 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(){
             var sym = node.scope.find_variable(name);
             if (!sym) {
                 var g;
-                if (HOP(globals, name)) {
+                if (globals[name]) {
                     g = globals[name];
                 } else {
                     g = new SymbolDef(self, node);
@@ -202,8 +202,8 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(){
 
 AST_Scope.DEFMETHOD("init_scope_vars", function(){
     this.directives = [];     // contains the directives defined in this scope, i.e. "use strict"
-    this.variables = {};      // map name to AST_SymbolVar (variables defined in this scope; includes functions)
-    this.functions = {};      // map name to AST_SymbolDefun (functions defined in this scope)
+    this.variables = Object.create(null); // map name to AST_SymbolVar (variables defined in this scope; includes functions)
+    this.functions = Object.create(null); // map name to AST_SymbolDefun (functions defined in this scope)
     this.uses_with = false;   // will be set to true if this or some nested scope uses the `with` statement
     this.uses_eval = false;   // will be set to true if this or nested scope uses the global `eval`
     this.parent_scope = null; // the parent scope
@@ -245,9 +245,8 @@ AST_LabelRef.DEFMETHOD("reference", function(){
 
 AST_Scope.DEFMETHOD("find_variable", function(name){
     if (name instanceof AST_Symbol) name = name.name;
-    return HOP(this.variables, name)
-        ? this.variables[name]
-        : (this.parent_scope && this.parent_scope.find_variable(name));
+    return this.variables[name]
+        || (this.parent_scope && this.parent_scope.find_variable(name));
 });
 
 AST_Scope.DEFMETHOD("has_directive", function(value){
@@ -261,7 +260,7 @@ AST_Scope.DEFMETHOD("def_function", function(symbol){
 
 AST_Scope.DEFMETHOD("def_variable", function(symbol){
     var def;
-    if (!HOP(this.variables, symbol.name)) {
+    if (!this.variables[symbol.name]) {
         def = new SymbolDef(this, symbol);
         this.variables[symbol.name] = def;
         def.global = !this.parent_scope;
@@ -351,7 +350,7 @@ AST_Toplevel.DEFMETHOD("mangle_names", function(options){
             var p = tw.parent();
             var is_setget = p instanceof AST_ObjectSetter || p instanceof AST_ObjectGetter;
             var a = node.variables;
-            for (var i in a) if (HOP(a, i)) {
+            for (var i in a) {
                 var symbol = a[i];
                 if (!(is_setget && symbol instanceof AST_SymbolLambda)) {
                     if (options.except.indexOf(symbol.name) < 0) {
@@ -450,15 +449,14 @@ var base54 = (function() {
     var string = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ$_0123456789";
     var chars, frequency;
     function reset() {
-        frequency = {};
+        frequency = Object.create(null);
         chars = string.split("");
         chars.map(function(ch){ frequency[ch] = 0 });
     }
     base54.consider = function(str){
         for (var i = str.length; --i >= 0;) {
             var ch = str.charAt(i);
-            if (string.indexOf(ch) >= 0)
-                ++frequency[ch];
+            ++frequency[ch];
         }
     };
     base54.sort = function() {