diff --git a/src/component/base/DraftEditor.react.js b/src/component/base/DraftEditor.react.js
index aa272305f2..df44bdd740 100644
--- a/src/component/base/DraftEditor.react.js
+++ b/src/component/base/DraftEditor.react.js
@@ -327,7 +327,11 @@ class DraftEditor extends React.Component<DraftEditorProps, State> {
      * ie9-beta-minor-change-list.aspx
      */
     if (isIE) {
-      document.execCommand('AutoUrlDetect', false, false);
+      ReactDOM.findDOMNode(this.refs.editor).ownerDocument.execCommand(
+        'AutoUrlDetect',
+        false,
+        false,
+      );
     }
   }
 
@@ -371,15 +375,13 @@ class DraftEditor extends React.Component<DraftEditorProps, State> {
     const scrollParent = Style.getScrollParent(editorNode);
     const {x, y} = scrollPosition || getScrollPosition(scrollParent);
 
-    invariant(
-      editorNode instanceof HTMLElement,
-      'editorNode is not an HTMLElement',
-    );
+    invariant(editorNode.nodeType === 1, 'editorNode is not an Element');
     editorNode.focus();
 
     // Restore scroll position
-    if (scrollParent === window) {
-      window.scrollTo(x, y);
+    const {defaultView} = editorNode.ownerDocument;
+    if (scrollParent === defaultView) {
+      defaultView.scrollTo(x, y);
     } else {
       Scroll.setTop(scrollParent, y);
     }
@@ -397,10 +399,7 @@ class DraftEditor extends React.Component<DraftEditorProps, State> {
 
   blur = (): void => {
     const editorNode = ReactDOM.findDOMNode(this.editor);
-    invariant(
-      editorNode instanceof HTMLElement,
-      'editorNode is not an HTMLElement',
-    );
+    invariant(editorNode.nodeType === 1, 'editorNode is not an Element');
     editorNode.blur();
   };
 
diff --git a/src/component/contents/DraftEditorBlock.react.js b/src/component/contents/DraftEditorBlock.react.js
index 2c62b8df54..6e9e50273f 100644
--- a/src/component/contents/DraftEditorBlock.react.js
+++ b/src/component/contents/DraftEditorBlock.react.js
@@ -102,26 +102,28 @@ class DraftEditorBlock extends React.Component<Props> {
     }
 
     const blockNode = ReactDOM.findDOMNode(this);
+    if (!blockNode || !blockNode.ownerDocument) {
+      return;
+    }
+
     const scrollParent = Style.getScrollParent(blockNode);
     const scrollPosition = getScrollPosition(scrollParent);
+    const win = blockNode.ownerDocument.defaultView;
     let scrollDelta;
 
-    if (scrollParent === window) {
+    if (scrollParent === win) {
       const nodePosition = getElementPosition(blockNode);
       const nodeBottom = nodePosition.y + nodePosition.height;
       const viewportHeight = getViewportDimensions().height;
       scrollDelta = nodeBottom - viewportHeight;
       if (scrollDelta > 0) {
-        window.scrollTo(
+        win.scrollTo(
           scrollPosition.x,
           scrollPosition.y + scrollDelta + SCROLL_BUFFER,
         );
       }
     } else {
-      invariant(
-        blockNode instanceof HTMLElement,
-        'blockNode is not an HTMLElement',
-      );
+      invariant(blockNode.nodeType === 1, 'blockNode is not an Element');
       const blockBottom = blockNode.offsetHeight + blockNode.offsetTop;
       const scrollBottom = scrollParent.offsetHeight + scrollPosition.y;
       scrollDelta = blockBottom - scrollBottom;
diff --git a/src/component/contents/DraftEditorTextNode.react.js b/src/component/contents/DraftEditorTextNode.react.js
index 50e3bfb5d4..e47972d22c 100644
--- a/src/component/contents/DraftEditorTextNode.react.js
+++ b/src/component/contents/DraftEditorTextNode.react.js
@@ -81,7 +81,7 @@ class DraftEditorTextNode extends React.Component<Props> {
   shouldComponentUpdate(nextProps: Props): boolean {
     const node = ReactDOM.findDOMNode(this);
     const shouldBeNewline = nextProps.children === '';
-    invariant(node instanceof Element, 'node is not an Element');
+    invariant(node.nodeType === 1, 'node is not an Element');
     if (shouldBeNewline) {
       return !isNewline(node);
     }
diff --git a/src/component/contents/exploration/DraftEditorBlockNode.react.js b/src/component/contents/exploration/DraftEditorBlockNode.react.js
index 40c6273a8b..d45377d0c6 100644
--- a/src/component/contents/exploration/DraftEditorBlockNode.react.js
+++ b/src/component/contents/exploration/DraftEditorBlockNode.react.js
@@ -237,26 +237,28 @@ class DraftEditorBlockNode extends React.Component<Props> {
     }
 
     const blockNode = ReactDOM.findDOMNode(this);
+    if (!blockNode || !blockNode.ownerDocument) {
+      return;
+    }
+
     const scrollParent = Style.getScrollParent(blockNode);
     const scrollPosition = getScrollPosition(scrollParent);
+    const win = blockNode.ownerDocument.defaultView;
     let scrollDelta;
 
-    if (scrollParent === window) {
+    if (scrollParent === win) {
       const nodePosition = getElementPosition(blockNode);
       const nodeBottom = nodePosition.y + nodePosition.height;
       const viewportHeight = getViewportDimensions().height;
       scrollDelta = nodeBottom - viewportHeight;
       if (scrollDelta > 0) {
-        window.scrollTo(
+        win.scrollTo(
           scrollPosition.x,
           scrollPosition.y + scrollDelta + SCROLL_BUFFER,
         );
       }
     } else {
-      invariant(
-        blockNode instanceof HTMLElement,
-        'blockNode is not an HTMLElement',
-      );
+      invariant(blockNode.nodeType === 1, 'blockNode is not an Element');
       const blockBottom = blockNode.offsetHeight + blockNode.offsetTop;
       const scrollBottom = scrollParent.offsetHeight + scrollPosition.y;
       scrollDelta = blockBottom - scrollBottom;
diff --git a/src/component/handlers/edit/editOnBlur.js b/src/component/handlers/edit/editOnBlur.js
index d96d751886..42d761bd51 100644
--- a/src/component/handlers/edit/editOnBlur.js
+++ b/src/component/handlers/edit/editOnBlur.js
@@ -20,7 +20,7 @@ const EditorState = require('EditorState');
 const containsNode = require('containsNode');
 const getActiveElement = require('getActiveElement');
 
-function editOnBlur(editor: DraftEditor, e: SyntheticEvent<>): void {
+function editOnBlur(editor: DraftEditor, e: SyntheticEvent<HTMLElement>): void {
   // In a contentEditable element, when you select a range and then click
   // another active element, this does trigger a `blur` event but will not
   // remove the DOM selection from the contenteditable.
@@ -29,8 +29,9 @@ function editOnBlur(editor: DraftEditor, e: SyntheticEvent<>): void {
   // We therefore force the issue to be certain, checking whether the active
   // element is `body` to force it when blurring occurs within the window (as
   // opposed to clicking to another tab or window).
-  if (getActiveElement() === document.body) {
-    const selection = global.getSelection();
+  const {ownerDocument} = e.currentTarget;
+  if (getActiveElement(ownerDocument) === ownerDocument.body) {
+    const selection = ownerDocument.defaultView.getSelection();
     const editorNode = editor.editor;
     if (
       selection.rangeCount === 1 &&
diff --git a/src/component/handlers/edit/editOnCut.js b/src/component/handlers/edit/editOnCut.js
index 575b9578a2..4eb3b7b3ef 100644
--- a/src/component/handlers/edit/editOnCut.js
+++ b/src/component/handlers/edit/editOnCut.js
@@ -31,11 +31,13 @@ const getScrollPosition = require('getScrollPosition');
  * In addition, we can keep a copy of the removed fragment, including all
  * styles and entities, for use as an internal paste.
  */
-function editOnCut(editor: DraftEditor, e: SyntheticClipboardEvent<>): void {
+function editOnCut(
+  editor: DraftEditor,
+  e: SyntheticClipboardEvent<HTMLElement>,
+): void {
   const editorState = editor._latestEditorState;
   const selection = editorState.getSelection();
-  const element = e.target;
-  let scrollPosition;
+  const element = e.currentTarget;
 
   // No selection, so there's nothing to cut.
   if (selection.isCollapsed()) {
@@ -45,9 +47,7 @@ function editOnCut(editor: DraftEditor, e: SyntheticClipboardEvent<>): void {
 
   // Track the current scroll position so that it can be forced back in place
   // after the editor regains control of the DOM.
-  if (element instanceof Node) {
-    scrollPosition = getScrollPosition(Style.getScrollParent(element));
-  }
+  const scrollPosition = getScrollPosition(Style.getScrollParent(element));
 
   const fragment = getFragmentFromSelection(editorState);
   editor.setClipboard(fragment);
diff --git a/src/component/handlers/edit/editOnInput.js b/src/component/handlers/edit/editOnInput.js
index 8d231287b6..3dbc8fa6a5 100644
--- a/src/component/handlers/edit/editOnInput.js
+++ b/src/component/handlers/edit/editOnInput.js
@@ -46,7 +46,8 @@ function editOnInput(editor: DraftEditor): void {
     editor._pendingStateFromBeforeInput = undefined;
   }
 
-  var domSelection = global.getSelection();
+  const editorNode = nullthrows(editor.editor);
+  const domSelection = editorNode.ownerDocument.defaultView.getSelection();
 
   var {anchorNode, isCollapsed} = domSelection;
   const isNotTextNode = anchorNode.nodeType !== Node.TEXT_NODE;
diff --git a/src/component/handlers/edit/editOnSelect.js b/src/component/handlers/edit/editOnSelect.js
index 88aa3d70d1..a089381c99 100644
--- a/src/component/handlers/edit/editOnSelect.js
+++ b/src/component/handlers/edit/editOnSelect.js
@@ -16,10 +16,9 @@
 import type DraftEditor from 'DraftEditor.react';
 
 var EditorState = require('EditorState');
-var ReactDOM = require('ReactDOM');
 
 var getDraftEditorSelection = require('getDraftEditorSelection');
-const invariant = require('invariant');
+const nullthrows = require('nullthrows');
 
 function editOnSelect(editor: DraftEditor): void {
   if (
@@ -30,16 +29,8 @@ function editOnSelect(editor: DraftEditor): void {
   }
 
   var editorState = editor.props.editorState;
-  const editorNode = ReactDOM.findDOMNode(editor.editorContainer);
-  invariant(editorNode, 'Missing editorNode');
-  invariant(
-    editorNode.firstChild instanceof HTMLElement,
-    'editorNode.firstChild is not an HTMLElement',
-  );
-  var documentSelection = getDraftEditorSelection(
-    editorState,
-    editorNode.firstChild,
-  );
+  const editorNode = nullthrows(editor.editor);
+  var documentSelection = getDraftEditorSelection(editorState, editorNode);
   var updatedSelectionState = documentSelection.selectionState;
 
   if (updatedSelectionState !== editorState.getSelection()) {
diff --git a/src/component/selection/expandRangeToStartOfLine.js b/src/component/selection/expandRangeToStartOfLine.js
index e889b05925..bdbcd1d251 100644
--- a/src/component/selection/expandRangeToStartOfLine.js
+++ b/src/component/selection/expandRangeToStartOfLine.js
@@ -30,7 +30,7 @@ function getLineHeightPx(element: Element): number {
   div.style.position = 'absolute';
   div.textContent = 'M';
 
-  let documentBody = document.body;
+  let documentBody = element.ownerDocument.body;
   invariant(documentBody, 'Missing document.body');
 
   // forced layout here
diff --git a/src/component/selection/findAncestorOffsetKey.js b/src/component/selection/findAncestorOffsetKey.js
index 45530b3372..de1c97efc8 100644
--- a/src/component/selection/findAncestorOffsetKey.js
+++ b/src/component/selection/findAncestorOffsetKey.js
@@ -20,7 +20,7 @@ var getSelectionOffsetKeyForNode = require('getSelectionOffsetKeyForNode');
  */
 function findAncestorOffsetKey(node: Node): ?string {
   let searchNode = node;
-  while (searchNode && searchNode !== document.documentElement) {
+  while (searchNode && searchNode.nodeName !== 'HTML') {
     var key = getSelectionOffsetKeyForNode(searchNode);
     if (key != null) {
       return key;
diff --git a/src/component/selection/getDraftEditorSelection.js b/src/component/selection/getDraftEditorSelection.js
index a9f7c16ede..cb2203fd12 100644
--- a/src/component/selection/getDraftEditorSelection.js
+++ b/src/component/selection/getDraftEditorSelection.js
@@ -26,7 +26,7 @@ function getDraftEditorSelection(
   editorState: EditorState,
   root: HTMLElement,
 ): DOMDerivedSelection {
-  var selection = global.getSelection();
+  var selection = root.ownerDocument.defaultView.getSelection();
 
   // No active selection.
   if (selection.rangeCount === 0) {
diff --git a/src/component/selection/getDraftEditorSelectionWithNodes.js b/src/component/selection/getDraftEditorSelectionWithNodes.js
index 7f28e6d66b..f5f1709814 100644
--- a/src/component/selection/getDraftEditorSelectionWithNodes.js
+++ b/src/component/selection/getDraftEditorSelectionWithNodes.js
@@ -169,7 +169,10 @@ function getPointForNonTextNode(
   if (editorRoot === node) {
     node = node.firstChild;
     invariant(
-      node instanceof Element && node.getAttribute('data-contents') === 'true',
+      node &&
+        node.nodeType === 1 &&
+        typeof node.getAttribute === 'function' &&
+        node.getAttribute('data-contents') === 'true',
       'Invalid DraftEditorContents structure.',
     );
     if (childOffset > 0) {
diff --git a/src/component/selection/getSelectionOffsetKeyForNode.js b/src/component/selection/getSelectionOffsetKeyForNode.js
index bc149bedd8..eabae39ed1 100644
--- a/src/component/selection/getSelectionOffsetKeyForNode.js
+++ b/src/component/selection/getSelectionOffsetKeyForNode.js
@@ -18,13 +18,14 @@
  * found on the DOM tree of given node.
  */
 function getSelectionOffsetKeyForNode(node: Node): ?string {
-  if (node instanceof Element) {
-    var offsetKey = node.getAttribute('data-offset-key');
+  if (node.nodeType === 1) {
+    var element: Element = (node: any);
+    var offsetKey = element.getAttribute('data-offset-key');
     if (offsetKey) {
       return offsetKey;
     }
-    for (var ii = 0; ii < node.childNodes.length; ii++) {
-      var childOffsetKey = getSelectionOffsetKeyForNode(node.childNodes[ii]);
+    for (var ii = 0; ii < element.childNodes.length; ii++) {
+      var childOffsetKey = getSelectionOffsetKeyForNode(element.childNodes[ii]);
       if (childOffsetKey) {
         return childOffsetKey;
       }
diff --git a/src/component/selection/setDraftEditorSelection.js b/src/component/selection/setDraftEditorSelection.js
index 98a79aee2e..8484ecbd62 100644
--- a/src/component/selection/setDraftEditorSelection.js
+++ b/src/component/selection/setDraftEditorSelection.js
@@ -35,10 +35,11 @@ function getAnonymizedDOM(
   }
 
   invariant(
-    anonymized instanceof Element,
+    anonymized.nodeType === Node.ELEMENT_NODE,
     'Node must be an Element if it is not a text node.',
   );
-  return anonymized.outerHTML;
+  var element: Element = (anonymized: any);
+  return element.outerHTML;
 }
 
 function anonymizeTextWithin(
@@ -76,15 +77,14 @@ function getAnonymizedEditorDOM(
   // grabbing the DOM content of the Draft editor
   let currentNode = node;
   while (currentNode) {
-    if (
-      currentNode instanceof Element &&
-      currentNode.hasAttribute('contenteditable')
-    ) {
-      // found the Draft editor container
-      return getAnonymizedDOM(currentNode, getNodeLabels);
-    } else {
-      currentNode = currentNode.parentNode;
+    if (currentNode.nodeType === 1) {
+      const currentElement: Element = (currentNode: any);
+      if (currentElement.hasAttribute('contenteditable')) {
+        // found the Draft editor container
+        return getAnonymizedDOM(currentNode, getNodeLabels);
+      }
     }
+    currentNode = currentNode.parentNode;
   }
   return 'Could not find contentEditable parent of node';
 }
@@ -111,14 +111,16 @@ function setDraftEditorSelection(
   nodeStart: number,
   nodeEnd: number,
 ): void {
+  var ownerDocument = node.ownerDocument;
+
   // It's possible that the editor has been removed from the DOM but
   // our selection code doesn't know it yet. Forcing selection in
   // this case may lead to errors, so just bail now.
-  if (!containsNode(document.documentElement, node)) {
+  if (!containsNode(ownerDocument.documentElement, node)) {
     return;
   }
 
-  var selection = global.getSelection();
+  var selection = ownerDocument.defaultView.getSelection();
   var anchorKey = selectionState.getAnchorKey();
   var anchorOffset = selectionState.getAnchorOffset();
   var focusKey = selectionState.getFocusKey();
@@ -234,7 +236,7 @@ function addFocusToSelection(
   offset: number,
   selectionState: SelectionState,
 ): void {
-  const activeElement = getActiveElement();
+  const activeElement = getActiveElement(node.ownerDocument);
   if (selection.extend && containsNode(activeElement, node)) {
     // If `extend` is called while another element has focus, an error is
     // thrown. We therefore disable `extend` if the active element is somewhere
@@ -315,7 +317,7 @@ function addPointToSelection(
   offset: number,
   selectionState: SelectionState,
 ): void {
-  var range = document.createRange();
+  var range = node.ownerDocument.createRange();
   // logging to catch bug that is being reported in t16250795
   if (offset > getNodeLength(node)) {
     // in this case we know that the call to 'range.setStart' is about to throw
diff --git a/src/model/encoding/convertFromHTMLToContentBlocks.js b/src/model/encoding/convertFromHTMLToContentBlocks.js
index 0b32f327a3..cf07fa9e6d 100644
--- a/src/model/encoding/convertFromHTMLToContentBlocks.js
+++ b/src/model/encoding/convertFromHTMLToContentBlocks.js
@@ -189,8 +189,8 @@ const processInlineTag = (
   const styleToCheck = inlineTags[tag];
   if (styleToCheck) {
     currentStyle = currentStyle.add(styleToCheck).toOrderedSet();
-  } else if (node instanceof HTMLElement) {
-    const htmlElement = node;
+  } else if (node.nodeType === 1) {
+    const htmlElement: HTMLElement = (node: any);
     currentStyle = currentStyle
       .withMutations(style => {
         const fontWeight = htmlElement.style.fontWeight;
@@ -274,11 +274,9 @@ const containsSemanticBlockMarkup = (
 };
 
 const hasValidLinkText = (link: Node): boolean => {
-  invariant(
-    link instanceof HTMLAnchorElement,
-    'Link must be an HTMLAnchorElement.',
-  );
-  const protocol = link.protocol;
+  invariant(link.nodeName === 'A', 'Link must be an HTMLAnchorElement.');
+  const element: HTMLAnchorElement = (link: any);
+  const {protocol} = element;
   return (
     protocol === 'http:' || protocol === 'https:' || protocol === 'mailto:'
   );
@@ -378,7 +376,7 @@ const genFragment = (
       text = text.replace(REGEX_LF, SPACE);
     }
 
-    // save the last block so we can use it later
+    // Save the last block so we can use it later
     lastBlock = nodeName;
 
     return {
@@ -392,7 +390,7 @@ const genFragment = (
     };
   }
 
-  // save the last block so we can use it later
+  // Save the last block so we can use it later
   lastBlock = nodeName;
 
   // BR tags
@@ -407,30 +405,30 @@ const genFragment = (
   }
 
   // IMG tags
-  if (
-    nodeName === 'img' &&
-    node instanceof HTMLImageElement &&
-    node.attributes.getNamedItem('src') &&
-    node.attributes.getNamedItem('src').value
-  ) {
-    const image: HTMLImageElement = node;
-    const entityConfig = {};
-
-    imgAttr.forEach(attr => {
-      const imageAttribute = image.getAttribute(attr);
-      if (imageAttribute) {
-        entityConfig[attr] = imageAttribute;
-      }
-    });
-    // Forcing this node to have children because otherwise no entity will be
-    // created for this node.
-    // The child text node cannot just have a space or return as content -
-    // we strip those out.
-    // See https://github.com/facebook/draft-js/issues/231 for some context.
-    node.textContent = '\ud83d\udcf7';
-
-    // TODO: update this when we remove DraftEntity entirely
-    inEntity = DraftEntity.__create('IMAGE', 'MUTABLE', entityConfig || {});
+  if (nodeName === 'img') {
+    const image: HTMLImageElement = (node: any);
+    if (
+      image.attributes.getNamedItem('src') &&
+      image.attributes.getNamedItem('src').value
+    ) {
+      const entityConfig = {};
+
+      imgAttr.forEach(attr => {
+        const imageAttribute = image.getAttribute(attr);
+        if (imageAttribute) {
+          entityConfig[attr] = imageAttribute;
+        }
+      });
+      // Forcing this node to have children because otherwise no entity will be
+      // created for this node.
+      // The child text node cannot just have a space or return as content -
+      // we strip those out.
+      // See https://github.com/facebook/draft-js/issues/231 for some context.
+      node.textContent = '\ud83d\udcf7';
+
+      // TODO: update this when we remove DraftEntity entirely
+      inEntity = DraftEntity.__create('IMAGE', 'MUTABLE', entityConfig || {});
+    }
   }
 
   // Inline tags
@@ -473,26 +471,23 @@ const genFragment = (
   let entityId: ?string = null;
 
   while (child) {
-    if (
-      child instanceof HTMLAnchorElement &&
-      child.href &&
-      hasValidLinkText(child)
-    ) {
-      const anchor: HTMLAnchorElement = child;
-      const entityConfig = {};
-
-      anchorAttr.forEach(attr => {
-        const anchorAttribute = anchor.getAttribute(attr);
-        if (anchorAttribute) {
-          entityConfig[attr] = anchorAttribute;
-        }
-      });
+    entityId = null;
+    if (nodeName === 'a') {
+      const anchor: HTMLAnchorElement = (child: any);
+      if (anchor.href && hasValidLinkText(anchor)) {
+        const entityConfig = {};
+
+        anchorAttr.forEach(attr => {
+          const anchorAttribute = anchor.getAttribute(attr);
+          if (anchorAttribute) {
+            entityConfig[attr] = anchorAttribute;
+          }
+        });
 
-      entityConfig.url = new URI(anchor.href).toString();
-      // TODO: update this when we remove DraftEntity completely
-      entityId = DraftEntity.__create('LINK', 'MUTABLE', entityConfig || {});
-    } else {
-      entityId = undefined;
+        entityConfig.url = new URI(anchor.href).toString();
+        // TODO: update this when we remove DraftEntity completely
+        entityId = DraftEntity.__create('LINK', 'MUTABLE', entityConfig || {});
+      }
     }
 
     const {