diff --git a/lib/svgo/jsAPI.js b/lib/svgo/jsAPI.js
index ea47b447..282ab6b4 100644
--- a/lib/svgo/jsAPI.js
+++ b/lib/svgo/jsAPI.js
@@ -305,8 +305,8 @@ JSAPI.prototype.renameElem = function(name) {
 
     if (!this.hasAttr()) return false;
 
-    for (var name in this.attrs) {
-        callback.call(context, this.attrs[name]);
+    for (const attr of Object.values(this.attrs)) {
+        callback.call(context, attr);
     }
 
     return true;
@@ -324,8 +324,8 @@ JSAPI.prototype.renameElem = function(name) {
 
     if (!this.hasAttr()) return false;
 
-    for (var name in this.attrs) {
-        if (callback.call(context, this.attrs[name])) return true;
+    for (const attr of Object.values(this.attrs)) {
+        if (callback.call(context, attr)) return true;
     }
 
     return false;
diff --git a/lib/svgo/svg2js.js b/lib/svgo/svg2js.js
index bdf9c6d4..83f46659 100644
--- a/lib/svgo/svg2js.js
+++ b/lib/svgo/svg2js.js
@@ -93,7 +93,7 @@ module.exports = function(data) {
         elem.style = new CSSStyleDeclaration(elem);
 
         if (Object.keys(data.attributes).length) {
-            for (var name in data.attributes) {
+            for (const [name, attr] of Object.entries(data.attributes)) {
 
                 if (name === 'class') { // has class attribute
                     elem.class.hasClass();
@@ -105,9 +105,9 @@ module.exports = function(data) {
 
                 elem.attrs[name] = {
                     name: name,
-                    value: data.attributes[name].value,
-                    prefix: data.attributes[name].prefix,
-                    local: data.attributes[name].local
+                    value: attr.value,
+                    prefix: attr.prefix,
+                    local: attr.local
                 };
             }
         }
diff --git a/plugins/minifyStyles.js b/plugins/minifyStyles.js
index d240900e..edae6b71 100755
--- a/plugins/minifyStyles.js
+++ b/plugins/minifyStyles.js
@@ -54,13 +54,7 @@ exports.fn = function(ast, options) {
 };
 
 function cloneObject(obj) {
-    var result = {};
-
-    for (var key in obj) {
-        result[key] = obj[key];
-    }
-
-    return result;
+    return {...obj};
 }
 
 function findStyleElems(ast) {
@@ -149,9 +143,9 @@ function collectUsageData(ast, options) {
         safe = true;
     }
 
-    for (var key in rawData) {
+    for (const [key, data] of Object.entries(rawData)) {
         if (shouldFilter(options, key)) {
-            usageData[key] = Object.keys(rawData[key]);
+            usageData[key] = Object.keys(data);
             hasData = true;
         }
     }
diff --git a/plugins/moveElemsAttrsToGroup.js b/plugins/moveElemsAttrsToGroup.js
index 2f3092e8..945643e9 100644
--- a/plugins/moveElemsAttrsToGroup.js
+++ b/plugins/moveElemsAttrsToGroup.js
@@ -63,7 +63,7 @@ exports.fn = function(item) {
 
             item.content.forEach(function(g) {
 
-                for (var name in intersection) {
+                for (const [name, attr] of Object.entries(intersection)) {
 
                     if (!allPath && !hasClip || name !== 'transform') {
 
@@ -72,15 +72,15 @@ exports.fn = function(item) {
                         if (name === 'transform') {
                             if (!hasTransform) {
                                 if (item.hasAttr('transform')) {
-                                    item.attr('transform').value += ' ' + intersection[name].value;
+                                    item.attr('transform').value += ' ' + attr.value;
                                 } else {
-                                    item.addAttr(intersection[name]);
+                                    item.addAttr(attr);
                                 }
 
                                 hasTransform = true;
                             }
                         } else {
-                            item.addAttr(intersection[name]);
+                            item.addAttr(attr);
                         }
 
                     }
@@ -106,17 +106,17 @@ function intersectInheritableAttrs(a, b) {
 
     var c = {};
 
-    for (var n in a) {
+    for (const [n, attr] of Object.entries(a)) {
         if (
             // eslint-disable-next-line no-prototype-builtins
             b.hasOwnProperty(n) &&
             inheritableAttrs.indexOf(n) > -1 &&
-            a[n].name === b[n].name &&
-            a[n].value === b[n].value &&
-            a[n].prefix === b[n].prefix &&
-            a[n].local === b[n].local
+            attr.name === b[n].name &&
+            attr.value === b[n].value &&
+            attr.prefix === b[n].prefix &&
+            attr.local === b[n].local
         ) {
-            c[n] = a[n];
+            c[n] = attr;
         }
     }
 
diff --git a/plugins/removeUnknownsAndDefaults.js b/plugins/removeUnknownsAndDefaults.js
index 31970a4f..1858b28b 100644
--- a/plugins/removeUnknownsAndDefaults.js
+++ b/plugins/removeUnknownsAndDefaults.js
@@ -25,9 +25,7 @@ var collections = require('./_collections'),
     applyGroups = collections.presentationNonInheritableGroupAttrs;
 
 // collect and extend all references
-for (var elem in elems) {
-    elem = elems[elem];
-
+for (const elem of Object.values(elems)) {
     if (elem.attrsGroups) {
         elem.attrs = elem.attrs || [];
 
@@ -39,8 +37,8 @@ for (var elem in elems) {
             if (groupDefaults) {
                 elem.defaults = elem.defaults || {};
 
-                for (var attrName in groupDefaults) {
-                    elem.defaults[attrName] = groupDefaults[attrName];
+                for (const [attrName, attr] of Object.entries(groupDefaults)) {
+                    elem.defaults[attrName] = attr;
                 }
             }
         });