Get rid of for-in loops

The for-in statement in JavaScript iterates also over inherited
properties. This is typically not desired and requires adding a
check using Object.prototype.hasOwnProperty inside the loop.

This commit replaces all for-in statements and related checks inside
them with iteration over Object.keys(...). The iteration is performed
using either Array.prototype.forEach of a plain for loop.

bin/pegjs

@@ -69,11 +69,9 @@ function addExtraOptions(options, json) {
     abort("The JSON with extra options has to represent an object.");
   }
 
-  for (let key in extraOptions) {
+  Object.keys(extraOptions).forEach(key => {
-    if (extraOptions.hasOwnProperty(key)) {
     options[key] = extraOptions[key];
-    }
+  });
-  }
 }
 
 /*

lib/compiler/index.js

@@ -67,11 +67,9 @@ let compiler = {
       trace:             false
     });
 
-    for (let stage in passes) {
+    Object.keys(passes).forEach(stage => {
-      if (passes.hasOwnProperty(stage)) {
       passes[stage].forEach(p => { p(ast, options); });
-      }
+    });
-    }
 
     switch (options.output) {
       case "parser": return eval(ast.code);

lib/peg.js

@@ -25,12 +25,10 @@ let peg = {
     function convertPasses(passes) {
       let converted = {};
 
-      for (let stage in passes) {
+      Object.keys(passes).forEach(stage => {
-        if (passes.hasOwnProperty(stage)) {
         converted[stage] = Object.keys(passes[stage])
           .map(name => passes[stage][name]);
-        }
+      });
-      }
 
       return converted;
     }

spec/behavior/generated-parser-behavior.spec.js

@@ -10,11 +10,9 @@ describe("generated parser behavior", function() {
     function clone(object) {
       let result = {};
 
-      for (let key in object) {
+      Object.keys(object).forEach(key => {
-        if (object.hasOwnProperty(key)) {
         result[key] = object[key];
-        }
+      });
-      }
 
       return result;
     }
@@ -89,8 +87,10 @@ describe("generated parser behavior", function() {
                 + jasmine.pp(e.message) + ".";
           } else {
             if (details) {
-              for (let key in details) {
+              let keys = Object.keys(details);
-                if (details.hasOwnProperty(key)) {
+              for (let i = 0; i < keys.length; i++) {
+                let key = keys[i];
+
                 if (!this.env.equals_(e[key], details[key])) {
                   this.message = () =>
                     "Expected " + jasmine.pp(input) + " "
@@ -105,7 +105,6 @@ describe("generated parser behavior", function() {
               }
             }
           }
-          }
 
           return true;
         }

spec/unit/compiler/passes/helpers.js

@@ -28,13 +28,14 @@ beforeEach(function() {
         } else if (isObject(details)) {
           if (!isObject(value)) { return false; }
 
-          for (let key in details) {
+          let keys = Object.keys(details);
-            if (details.hasOwnProperty(key)) {
+          for (let i = 0; i < keys.length; i++) {
+            let key = keys[i];
+
             if (!(key in value)) { return false; }
 
             if (!matchDetails(value[key], details[key])) { return false; }
           }
-          }
 
           return true;
         } else {
@@ -70,8 +71,10 @@ beforeEach(function() {
               + "but it did.";
         } else {
           if (details) {
-            for (let key in details) {
+            let keys = Object.keys(details);
-              if (details.hasOwnProperty(key)) {
+            for (let i = 0; i < keys.length; i++) {
+              let key = keys[i];
+
               if (!this.env.equals_(e[key], details[key])) {
                 this.message = () =>
                   "Expected the pass to report an error "
@@ -85,7 +88,6 @@ beforeEach(function() {
             }
           }
         }
-        }
 
         return true;
       }

spec/unit/parser.spec.js

@@ -204,8 +204,10 @@ describe("PEG.js grammar parser", function() {
                 + jasmine.pp(e.message) + ".";
           } else {
             if (details) {
-              for (let key in details) {
+              let keys = Object.keys(details);
-                if (details.hasOwnProperty(key)) {
+              for (let i = 0; i < keys.length; i++) {
+                let key = keys[i];
+
                 if (!this.env.equals_(e[key], details[key])) {
                   this.message = () =>
                     "Expected " + jasmine.pp(this.actual) + " to fail to parse"
@@ -218,7 +220,6 @@ describe("PEG.js grammar parser", function() {
               }
             }
           }
-          }
 
           return true;
         }