diff --git a/package.json b/package.json
index b6ff9281e..c98c7a14d 100644
--- a/package.json
+++ b/package.json
@@ -16,6 +16,7 @@
     "is-in-browser": "^1.1.3",
     "is-window": "^1.0.2",
     "keycode": "^2.1.2",
+    "lodash": "^4.17.4",
     "prop-types": "^15.5.8",
     "react-portal": "^3.1.0",
     "selection-is-backward": "^1.0.0",
diff --git a/src/components/editor.js b/src/components/editor.js
index 25755c6b1..b521e518a 100644
--- a/src/components/editor.js
+++ b/src/components/editor.js
@@ -125,7 +125,8 @@ class Editor extends React.Component {
     this.state.state = state
 
     // Create a bound event handler for each event.
-    for (const method of EVENT_HANDLERS) {
+    for (let i = 0; i < EVENT_HANDLERS.length; i++) {
+      const method = EVENT_HANDLERS[i]
       this[method] = (...args) => {
         const next = this.state.stack[method](this.state.state, this, ...args)
         this.onChange(next)
@@ -144,7 +145,8 @@ class Editor extends React.Component {
     let { stack } = this.state
 
     // If any plugin-related properties will change, create a new `Stack`.
-    for (const prop of PLUGINS_PROPS) {
+    for (let i = 0; i < PLUGINS_PROPS.length; i++) {
+      const prop = PLUGINS_PROPS[i]
       if (props[prop] == this.props[prop]) continue
       const { onChange, ...rest } = props // eslint-disable-line no-unused-vars
       stack = Stack.create(rest)
@@ -259,7 +261,8 @@ class Editor extends React.Component {
  * Mix in the property types for the event handlers.
  */
 
-for (const property of EVENT_HANDLERS) {
+for (let i = 0; i < EVENT_HANDLERS.length; i++) {
+  const property = EVENT_HANDLERS[i]
   Editor.propTypes[property] = Types.func
 }
 
diff --git a/src/constants/environment.js b/src/constants/environment.js
index 0a4e61655..7fb075aa3 100644
--- a/src/constants/environment.js
+++ b/src/constants/environment.js
@@ -48,16 +48,16 @@ let OS
 if (browser) {
   const { userAgent } = window.navigator
 
-  for (const rule of BROWSER_RULES) {
-    const [ name, regexp ] = rule
+  for (let i = 0; i < BROWSER_RULES.length; i++) {
+    const [ name, regexp ] = BROWSER_RULES[i]
     if (regexp.test(userAgent)) {
       BROWSER = name
       break
     }
   }
 
-  for (const rule of OS_RULES) {
-    const [ name, regexp ] = rule
+  for (let i = 0; i < OS_RULES.length; i++) {
+    const [ name, regexp ] = OS_RULES[i]
     if (regexp.test(userAgent)) {
       OS = name
       break
diff --git a/src/models/node.js b/src/models/node.js
index b1bb44649..864c8183e 100644
--- a/src/models/node.js
+++ b/src/models/node.js
@@ -526,7 +526,8 @@ const Node = {
   getDescendantAtPath(path) {
     let descendant = this
 
-    for (const index of path) {
+    for (let i = 0; i < path.length; i++) {
+      const index = path[i]
       if (!descendant) return
       if (!descendant.nodes) return
       descendant = descendant.nodes.get(index)
diff --git a/src/models/schema.js b/src/models/schema.js
index 9e8ead4c2..db869a72f 100644
--- a/src/models/schema.js
+++ b/src/models/schema.js
@@ -4,6 +4,7 @@ import isReactComponent from '../utils/is-react-component'
 import typeOf from 'type-of'
 import MODEL_TYPES from '../constants/model-types'
 import { Record } from 'immutable'
+import find from 'lodash/find'
 
 /**
  * Default properties.
@@ -90,7 +91,7 @@ class Schema extends new Record(DEFAULTS) {
    */
 
   __getComponent(object) {
-    const match = this.rules.find(rule => rule.render && rule.match(object))
+    const match = find(this.rules, rule => rule.render && rule.match(object))
     if (!match) return
     return match.render
   }
@@ -131,7 +132,7 @@ class Schema extends new Record(DEFAULTS) {
   __validate(object) {
     let value
 
-    const match = this.rules.find((rule) => {
+    const match = find(this.rules, (rule) => {
       if (!rule.validate) return
       if (!rule.match(object)) return
 
diff --git a/src/models/stack.js b/src/models/stack.js
index 8ff85c553..a06709048 100644
--- a/src/models/stack.js
+++ b/src/models/stack.js
@@ -102,7 +102,8 @@ class Stack extends new Record(DEFAULTS) {
     const plugins = this.plugins.slice().reverse()
     let children
 
-    for (const plugin of plugins) {
+    for (let i = 0; i < plugins.length; i++) {
+      const plugin = plugins[i]
       if (!plugin.render) continue
       children = plugin.render(props, state, editor)
       props.children = children
@@ -123,7 +124,8 @@ class Stack extends new Record(DEFAULTS) {
     debug('renderPortal')
     const portals = []
 
-    for (const plugin of this.plugins) {
+    for (let i = 0; i < this.plugins.length; i++) {
+      const plugin = this.plugins[i]
       if (!plugin.renderPortal) continue
       const portal = plugin.renderPortal(state, editor)
       if (portal == null) continue
@@ -144,11 +146,13 @@ class Stack extends new Record(DEFAULTS) {
  * @return {State|Null}
  */
 
-for (const method of EVENT_HANDLER_METHODS) {
+for (let i = 0; i < EVENT_HANDLER_METHODS.length; i++) {
+  const method = EVENT_HANDLER_METHODS[i]
   Stack.prototype[method] = function (state, editor, ...args) {
     debug(method)
 
-    for (const plugin of this.plugins) {
+    for (let k = 0; k < this.plugins.length; k++) {
+      const plugin = this.plugins[k]
       if (!plugin[method]) continue
       const next = plugin[method](...args, state, editor)
       if (next == null) continue
@@ -169,7 +173,8 @@ for (const method of EVENT_HANDLER_METHODS) {
  * @return {State|Null}
  */
 
-for (const method of STATE_ACCUMULATOR_METHODS) {
+for (let i = 0; i < STATE_ACCUMULATOR_METHODS.length; i++) {
+  const method = STATE_ACCUMULATOR_METHODS[i]
   Stack.prototype[method] = function (state, editor, ...args) {
     debug(method)
 
@@ -177,7 +182,8 @@ for (const method of STATE_ACCUMULATOR_METHODS) {
       state = this.onBeforeChange(state, editor)
     }
 
-    for (const plugin of this.plugins) {
+    for (let k = 0; k < this.plugins.length; k++) {
+      const plugin = this.plugins[k]
       if (!plugin[method]) continue
       const next = plugin[method](...args, state, editor)
       if (next == null) continue
@@ -210,7 +216,8 @@ function assertState(value) {
 function resolveSchema(plugins) {
   let rules = []
 
-  for (const plugin of plugins) {
+  for (let i = 0; i < plugins.length; i++) {
+    const plugin = plugins[i]
     if (plugin.schema == null) continue
     const schema = Schema.create(plugin.schema)
     rules = rules.concat(schema.rules)
diff --git a/src/models/text.js b/src/models/text.js
index 063caae88..b73404ad4 100644
--- a/src/models/text.js
+++ b/src/models/text.js
@@ -167,7 +167,8 @@ class Text extends new Record(DEFAULTS) {
     let { characters } = node
     if (characters.size == 0) return characters
 
-    for (const decorator of decorators) {
+    for (let i = 0; i < decorators.length; i++) {
+      const decorator = decorators[i]
       const decorateds = decorator(node)
       characters = characters.merge(decorateds)
     }
diff --git a/src/serializers/html.js b/src/serializers/html.js
index f62d816b1..c868c610a 100644
--- a/src/serializers/html.js
+++ b/src/serializers/html.js
@@ -219,7 +219,8 @@ class Html {
       }
     }
 
-    for (const rule of this.rules) {
+    for (let i = 0; i < this.rules.length; i++) {
+      const rule = this.rules[i]
       if (!rule.deserialize) continue
       const ret = rule.deserialize(element, next)
       const type = typeOf(ret)
@@ -311,7 +312,8 @@ class Html {
 
     const children = node.nodes.map(this.serializeNode)
 
-    for (const rule of this.rules) {
+    for (let i = 0; i < this.rules.length; i++) {
+      const rule = this.rules[i]
       if (!rule.serialize) continue
       const ret = rule.serialize(node, children)
       if (ret) return addKey(ret)
@@ -332,7 +334,8 @@ class Html {
     const text = this.serializeString(string)
 
     return range.marks.reduce((children, mark) => {
-      for (const rule of this.rules) {
+      for (let i = 0; i < this.rules.length; i++) {
+        const rule = this.rules[i]
         if (!rule.serialize) continue
         const ret = rule.serialize(mark, children)
         if (ret) return addKey(ret)
@@ -350,7 +353,8 @@ class Html {
    */
 
   serializeString = (string) => {
-    for (const rule of this.rules) {
+    for (let i = 0; i < this.rules.length; i++) {
+      const rule = this.rules[i]
       if (!rule.serialize) continue
       const ret = rule.serialize(string, string.text)
       if (ret) return ret
diff --git a/src/utils/memoize.js b/src/utils/memoize.js
index e7096b786..12b10bc8d 100644
--- a/src/utils/memoize.js
+++ b/src/utils/memoize.js
@@ -56,7 +56,8 @@ const UNSET = undefined
 function memoize(object, properties, options = {}) {
   const { takesArguments = true } = options
 
-  for (const property of properties) {
+  for (let i = 0; i < properties.length; i++) {
+    const property = properties[i]
     const original = object[property]
 
     if (!original) {
@@ -121,7 +122,8 @@ function memoize(object, properties, options = {}) {
  */
 
 function getIn(map, keys) {
-  for (const key of keys) {
+  for (let i = 0; i < keys.length; i++) {
+    const key = keys[i]
     map = map.get(key)
     if (map === UNSET) return UNSET
   }
@@ -142,7 +144,8 @@ function setIn(map, keys, value) {
   let parent = map
   let child
 
-  for (const key of keys) {
+  for (let i = 0; i < keys.length; i++) {
+    const key = keys[i]
     child = parent.get(key)
 
     // If the path was not created yet...
diff --git a/yarn.lock b/yarn.lock
index 587b49004..568458884 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -3963,7 +3963,7 @@ lodash.pickby@^4.0.0:
   version "4.6.0"
   resolved "https://registry.yarnpkg.com/lodash.pickby/-/lodash.pickby-4.6.0.tgz#7dea21d8c18d7703a27c704c15d3b84a67e33aff"
 
-lodash@^4.0.0, lodash@^4.14.0, lodash@^4.2.0, lodash@^4.3.0:
+lodash@^4.0.0, lodash@^4.14.0, lodash@^4.17.4, lodash@^4.2.0, lodash@^4.3.0:
   version "4.17.4"
   resolved "https://registry.yarnpkg.com/lodash/-/lodash-4.17.4.tgz#78203a4d1c328ae1d86dca6460e369b57f4055ae"