diff --git a/examples/arithmetics.pegjs b/examples/arithmetics.pegjs
index dc2bc49..d2be1ab 100644
--- a/examples/arithmetics.pegjs
+++ b/examples/arithmetics.pegjs
@@ -5,17 +5,17 @@
 
 Expression
   = head:Term tail:(_ @("+" / "-") _ @Term)* {
-      return tail.reduce(function(result, [operator, factor]) {
-        if (operator === "+") return result + factor;
-        if (operator === "-") return result - factor;
+      return tail.reduce(function(result, element) {
+        if (element[0] === "+") return result + element[1];
+        if (element[0] === "-") return result - element[1];
       }, head);
     }
 
 Term
   = head:Factor tail:(_ @("*" / "/") _ @Factor)* {
-      return tail.reduce(function(result, [operator, factor]) {
-        if (operator === "*") return result * factor;
-        if (operator === "/") return result / factor;
+      return tail.reduce(function(result, element) {
+        if (element[0] === "*") return result * element[1];
+        if (element[0] === "/") return result / element[1];
       }, head);
     }
 
diff --git a/packages/pegjs/lib/ast/Grammar.js b/packages/pegjs/lib/ast/Grammar.js
index 9000030..0300695 100644
--- a/packages/pegjs/lib/ast/Grammar.js
+++ b/packages/pegjs/lib/ast/Grammar.js
@@ -27,21 +27,13 @@ class Grammar extends Node {
 
     findRule( name ) {
 
-        return this.rules.find( rule => rule.name === name );
+        return util.find( this.rules, rule => rule.name === name );
 
     }
 
     indexOfRule( name ) {
 
-        const rules = this.rules;
-
-        for ( let i = 0; i < rules.length; ++i ) {
-
-            if ( rules[ i ].name === name ) return i;
-
-        }
-
-        return -1;
+        return util.findIndex( this.rules, rule => rule.name === name );
 
     }
 
diff --git a/packages/pegjs/lib/compiler/index.js b/packages/pegjs/lib/compiler/index.js
index a2b14e2..4d44bd4 100644
--- a/packages/pegjs/lib/compiler/index.js
+++ b/packages/pegjs/lib/compiler/index.js
@@ -67,6 +67,9 @@ const compiler = {
             trace: false
         } );
 
+        // We want `session.vm.runInContext` to return the parser
+        if ( options.output === "parser" ) options.format = "bare";
+
         util.each( session.passes, stage => {
 
             stage.forEach( pass => {
diff --git a/packages/pegjs/lib/compiler/passes/generate-bytecode.js b/packages/pegjs/lib/compiler/passes/generate-bytecode.js
index fc6d713..8278edb 100644
--- a/packages/pegjs/lib/compiler/passes/generate-bytecode.js
+++ b/packages/pegjs/lib/compiler/passes/generate-bytecode.js
@@ -222,7 +222,7 @@ function generateBytecode( ast, session ) {
             ignoreCase: node.ignoreCase
         };
         const pattern = JSON.stringify( cls );
-        const index = classes.findIndex( c => JSON.stringify( c ) === pattern );
+        const index = util.findIndex( classes, c => JSON.stringify( c ) === pattern );
         return index === -1 ? classes.push( cls ) - 1 : index;
 
     }
@@ -230,7 +230,7 @@ function generateBytecode( ast, session ) {
     function addExpectedConst( expected ) {
 
         const pattern = JSON.stringify( expected );
-        const index = expectations.findIndex( e => JSON.stringify( e ) === pattern );
+        const index = util.findIndex( expectations, e => JSON.stringify( e ) === pattern );
         return index === -1 ? expectations.push( expected ) - 1 : index;
 
     }
@@ -239,7 +239,7 @@ function generateBytecode( ast, session ) {
 
         const func = { predicate: predicate, params: params, body: code };
         const pattern = JSON.stringify( func );
-        const index = functions.findIndex( f => JSON.stringify( f ) === pattern );
+        const index = util.findIndex( functions, f => JSON.stringify( f ) === pattern );
         return index === -1 ? functions.push( func ) - 1 : index;
 
     }
diff --git a/packages/pegjs/lib/compiler/passes/remove-proxy-rules.js b/packages/pegjs/lib/compiler/passes/remove-proxy-rules.js
index d40b3b0..2365a05 100644
--- a/packages/pegjs/lib/compiler/passes/remove-proxy-rules.js
+++ b/packages/pegjs/lib/compiler/passes/remove-proxy-rules.js
@@ -22,18 +22,18 @@ function removeProxyRules( ast, session, options ) {
     const allowedStartRules = options.allowedStartRules;
     const rules = [];
 
-    for ( const rule of ast.rules ) {
+    ast.rules.forEach( rule => {
 
         if ( isProxyRule( rule ) ) {
 
             replaceRuleRefs( ast, rule.name, rule.expression.name );
-            if ( allowedStartRules.indexOf( rule.name ) < 0 ) continue;
+            if ( allowedStartRules.indexOf( rule.name ) < 0 ) return;
 
         }
 
         rules.push( rule );
 
-    }
+    } );
 
     ast.rules = rules;
 
diff --git a/packages/pegjs/lib/parser.js b/packages/pegjs/lib/parser.js
index 49b45e9..111d468 100644
--- a/packages/pegjs/lib/parser.js
+++ b/packages/pegjs/lib/parser.js
@@ -3414,11 +3414,11 @@ function peg$parse(input, options) {
 
       // Populate `RESERVED_WORDS` using the optional option `reservedWords`
       const reservedWords = options.reservedWords || util.reservedWords;
-      if ( Array.isArray( reservedWords ) ) {
+      if ( Array.isArray( reservedWords ) ) reservedWords.forEach( word => {
 
-          for ( const word of reservedWords ) RESERVED_WORDS[ word ] = true;
+          RESERVED_WORDS[ word ] = true;
 
-      }
+      } );
 
       // Helper to construct a new AST Node
       function createNode( type, details ) {
diff --git a/packages/pegjs/lib/util/arrays.js b/packages/pegjs/lib/util/arrays.js
new file mode 100644
index 0000000..f8b4390
--- /dev/null
+++ b/packages/pegjs/lib/util/arrays.js
@@ -0,0 +1,33 @@
+"use strict";
+
+/**
+ * The `findIndex()` method returns the index of the first element in the array that satisfies the
+ * provided testing function, otherwise `-1` is returned.
+ */
+function findIndex( array, condition ) {
+
+    for ( let i = 0; i < array.length; ++i ) {
+
+        if ( condition( array[ i ], i ) ) return i;
+
+    }
+
+    return -1;
+
+}
+
+/**
+ * The `find()` method returns the value of the first element in the array that satisfies the
+ * provided testing function, otherwise `undefined` is returned.
+ */
+function find( array, condition ) {
+
+    const index = findIndex( array, condition );
+
+    return index < 0 ? void 0 : array[ index ];
+
+}
+
+// Exports
+
+module.exports = { findIndex, find };
diff --git a/packages/pegjs/lib/util/index.js b/packages/pegjs/lib/util/index.js
index 9b72348..3d39ff8 100644
--- a/packages/pegjs/lib/util/index.js
+++ b/packages/pegjs/lib/util/index.js
@@ -1,9 +1,11 @@
 "use strict";
 
+const arrays = require( "./arrays" );
 const js = require( "./js" );
 const objects = require( "./objects" );
 const vm = require( "./vm" );
 
+objects.extend( exports, arrays );
 objects.extend( exports, js );
 objects.extend( exports, objects );
 objects.extend( exports, vm );
diff --git a/packages/pegjs/lib/util/vm.js b/packages/pegjs/lib/util/vm.js
index 28fe03f..4e9beaa 100644
--- a/packages/pegjs/lib/util/vm.js
+++ b/packages/pegjs/lib/util/vm.js
@@ -1,58 +1,26 @@
 "use strict";
 
-const code = ( () => {
+/**
+ * `eval` the given source, using properties found in `context` as top-level variables.
+ * 
+ * Based on `vm.runInContext` found in Node.js, this is a cross-env solution.
+ */
+function runInContext( source, context ) {
 
-    let preface = "";
-    const MODULE_VARS = {
+    const argumentKeys = Object.keys( context );
+    const argumentValues = argumentKeys.map( argument => context[ argument ] );
 
-        "module": true,
-        "process": true,
-        "code": true,
-        "runInContext": true,
-        "source": true,
-        "preface": true,
+    const object = {};
+    argumentKeys.push( "_peg$object", `_peg$object.result = ${ source };` );
+    argumentValues.push( object );
 
-    };
+    Function( ...argumentKeys )( ...argumentValues );
 
-    Object.keys( MODULE_VARS ).forEach( name => {
+    return object.result;
 
-        preface += `var ${ name } = void 0;`;
 
-    } );
+}
 
-    function generate( name ) {
+// Exports
 
-        return `${ ( MODULE_VARS[ name ] ? "" : "var " ) + name } = __context.${ name };`;
-
-    }
-
-    return { generate, preface };
-
-} )();
-
-module.exports = {
-
-    // `eval` the given source, using properties found in `context` as top-level
-    // variables, while hiding some variables in this module from the source.
-    //
-    // Based on `vm.runInContext` found in Node.js, this is a cross-env solution.
-    runInContext( source, __context ) {
-
-        let preface = code.preface;
-
-        if ( typeof __context === "object" ) {
-
-            Object.keys( __context ).forEach( name => {
-
-                preface += code.generate( name );
-
-            } );
-
-        }
-
-        return eval( preface + source );
-
-
-    },
-
-};
+module.exports = { runInContext };
diff --git a/packages/pegjs/typings/api.d.ts b/packages/pegjs/typings/api.d.ts
index 661463f..defcc37 100644
--- a/packages/pegjs/typings/api.d.ts
+++ b/packages/pegjs/typings/api.d.ts
@@ -435,7 +435,7 @@ declare namespace peg {
 
         interface ISessionVM {
 
-            runInContext( code: string, vm$context?: { [ name: string ]: any; } ): any;
+            runInContext( code: string, context?: { [ name: string ]: any; } ): any;
 
         }
 
@@ -537,6 +537,12 @@ declare namespace peg {
 
     }
 
+    interface IArrayUtils {
+
+        findIndex( array: any[], condition: IIterator ): number;
+        find( array: any[], condition: IIterator ): any;
+
+    }
     interface IJavaScriptUtils {
 
         stringEscape( s: string ): string;
@@ -554,7 +560,7 @@ declare namespace peg {
         enforceFastProperties( o: {} ): {};
 
     }
-    interface util extends IJavaScriptUtils, IObjectUtils, compiler.ISessionVM {
+    interface util extends IArrayUtils, IJavaScriptUtils, IObjectUtils, compiler.ISessionVM {
 
         noop(): void;
         convertPasses( stages: IStageMap ): compiler.IPassesMap;
diff --git a/packages/pegjs/typings/modules.d.ts b/packages/pegjs/typings/modules.d.ts
index 8baa223..c51f986 100644
--- a/packages/pegjs/typings/modules.d.ts
+++ b/packages/pegjs/typings/modules.d.ts
@@ -151,6 +151,13 @@ declare module "pegjs/lib/util" {
 
 }
 
+declare module "pegjs/lib/util/arrays" {
+
+    const arrays: peg.IArrayUtils;
+    export default arrays;
+
+}
+
 declare module "pegjs/lib/util/index" {
 
     export default peg.util;
diff --git a/src/parser.pegjs b/src/parser.pegjs
index e299c27..feb2b8e 100644
--- a/src/parser.pegjs
+++ b/src/parser.pegjs
@@ -31,11 +31,11 @@
 
     // Populate `RESERVED_WORDS` using the optional option `reservedWords`
     const reservedWords = options.reservedWords || util.reservedWords;
-    if ( Array.isArray( reservedWords ) ) {
+    if ( Array.isArray( reservedWords ) ) reservedWords.forEach( word => {
 
-        for ( const word of reservedWords ) RESERVED_WORDS[ word ] = true;
+        RESERVED_WORDS[ word ] = true;
 
-    }
+    } );
 
     // Helper to construct a new AST Node
     function createNode( type, details ) {