diff --git a/js/cpu6502.js b/js/cpu6502.js
index 726b839..fa97340 100644
--- a/js/cpu6502.js
+++ b/js/cpu6502.js
@@ -1263,11 +1263,7 @@ export default function CPU6502(options)
     };
 
     if (is65C02) {
-        for (var key in cops) {
-            if (cops.hasOwnProperty(key)) {
-                ops[key] = cops[key];
-            }
-        }
+        Object.assign(ops, cops);
     }
 
     function unknown(b) {
diff --git a/js/mmu.js b/js/mmu.js
index 923bd62..18eefc1 100644
--- a/js/mmu.js
+++ b/js/mmu.js
@@ -134,11 +134,9 @@ export default function MMU(cpu, vm, lores1, lores2, hires1, hires2, io, rom)
     function Switches() {
         var locs = {};
 
-        for (var loc in LOC) {
-            if (LOC.hasOwnProperty(loc)) {
-                locs[LOC[loc]] = loc;
-            }
-        }
+        Object.keys(LOC).forEach(function(loc) {
+            locs[LOC[loc]] = loc;
+        });
 
         return {
             start: function() {
diff --git a/js/ui/apple2.js b/js/ui/apple2.js
index 0750eed..1b126bd 100644
--- a/js/ui/apple2.js
+++ b/js/ui/apple2.js
@@ -472,13 +472,7 @@ function loadDisk(drive, disk) {
 
 function updateLocalStorage() {
     var diskIndex = JSON.parse(window.localStorage.diskIndex || '{}');
-    var names = [], name, cat;
-
-    for (name in diskIndex) {
-        if (diskIndex.hasOwnProperty(name)) {
-            names.push(name);
-        }
-    }
+    var names = Object.keys(diskIndex), cat;
 
     cat = disk_categories['Local Saves'] = [];
     document.querySelector('#manage-modal-content').innerHTML = '';
diff --git a/js/util.js b/js/util.js
index 9e83724..e68a9af 100644
--- a/js/util.js
+++ b/js/util.js
@@ -97,20 +97,6 @@ export function hup() {
         return results[1];
 }
 
-export function keys(obj) {
-    var result = [];
-    for (var key in obj) {
-        if (obj.hasOwnProperty(key)) {
-            result.push(key);
-        }
-    }
-    return result;
-}
-
-export function each(obj, fn) {
-    keys(obj).forEach(fn);
-}
-
 export function numToString(num) {
     let result = '';
     for (let idx = 0; idx < 4; idx++) {