diff --git a/client/modules/IDE/components/Editor.jsx b/client/modules/IDE/components/Editor.jsx
index e90d1c19..9bfcf0d2 100644
--- a/client/modules/IDE/components/Editor.jsx
+++ b/client/modules/IDE/components/Editor.jsx
@@ -40,11 +40,9 @@ class Editor extends React.Component {
     this.widgets = [];
     this._cm = CodeMirror(this.refs.container, { // eslint-disable-line
       theme: `p5-${this.props.theme}`,
-      value: this.props.file.content,
       lineNumbers: true,
       styleActiveLine: true,
       inputStyle: 'contenteditable',
-      mode: 'javascript',
       lineWrapping: false,
       fixedGutter: false,
       gutters: ['CodeMirror-lint-markers'],
@@ -64,6 +62,9 @@ class Editor extends React.Component {
       }
     });
 
+    this.initializeDocuments(this.props.files);
+    this._cm.swapDoc(this._docs[this.props.file.id]);
+
     this._cm.on('change', debounce(() => {
       this.props.setUnsavedChanges(true);
       this.props.updateFileContent(this.props.file.name, this._cm.getValue());
@@ -89,10 +90,20 @@ class Editor extends React.Component {
     this._cm.setOption('tabSize', this.props.indentationAmount);
   }
 
+  componentWillUpdate(nextProps) {
+    // check if files have changed
+    if (this.props.files[0].id !== nextProps.files[0].id) {
+      // then need to make CodeMirror documents
+      this.initializeDocuments(nextProps.files);
+    }
+  }
+
   componentDidUpdate(prevProps) {
     if (this.props.file.content !== prevProps.file.content &&
         this.props.file.content !== this._cm.getValue()) {
-      this._cm.setValue(this.props.file.content); // eslint-disable-line no-underscore-dangle
+      const oldDoc = this._cm.swapDoc(this._docs[this.props.file.id]);
+      this._docs[prevProps.file.id] = oldDoc;
+      this._cm.focus();
       if (!prevProps.unsavedChanges) {
         setTimeout(() => this.props.setUnsavedChanges(false), 400);
       }
@@ -106,20 +117,6 @@ class Editor extends React.Component {
     if (this.props.isTabIndent !== prevProps.isTabIndent) {
       this._cm.setOption('indentWithTabs', this.props.isTabIndent);
     }
-    if (this.props.file.name !== prevProps.name) {
-      if (this.props.file.name.match(/.+\.js$/i)) {
-        this._cm.setOption('mode', 'javascript');
-      } else if (this.props.file.name.match(/.+\.css$/i)) {
-        this._cm.setOption('mode', 'css');
-      } else if (this.props.file.name.match(/.+\.html$/i)) {
-        this._cm.setOption('mode', 'htmlmixed');
-      } else if (this.props.file.name.match(/.+\.json$/i)) {
-        this._cm.setOption('mode', 'application/json');
-      } else {
-        this._cm.setOption('mode', 'text/plain');
-      }
-    }
-
     if (this.props.theme !== prevProps.theme) {
       this._cm.setOption('theme', `p5-${this.props.theme}`);
     }
@@ -129,6 +126,31 @@ class Editor extends React.Component {
     this._cm = null;
   }
 
+  getFileMode(fileName) {
+    let mode;
+    if (fileName.match(/.+\.js$/i)) {
+      mode = 'javascript';
+    } else if (fileName.match(/.+\.css$/i)) {
+      mode = 'css';
+    } else if (fileName.match(/.+\.html$/i)) {
+      mode = 'htmlmixed';
+    } else if (fileName.match(/.+\.json$/i)) {
+      mode = 'application/json';
+    } else {
+      mode = 'text/plain';
+    }
+    return mode;
+  }
+
+  initializeDocuments(files) {
+    this._docs = {};
+    files.forEach(file => {
+      if (file.fileType === 'file') {
+        this._docs[file.id] = CodeMirror.Doc(file.content, this.getFileMode(file.name)); // eslint-disable-line
+      }
+    });
+  }
+
   tidyCode() {
     const beautifyOptions = {
       indent_size: this.props.indentationAmount,
@@ -211,7 +233,8 @@ Editor.propTypes = {
   fontSize: PropTypes.number.isRequired,
   file: PropTypes.shape({
     name: PropTypes.string.isRequired,
-    content: PropTypes.string.isRequired
+    content: PropTypes.string.isRequired,
+    id: PropTypes.string.isRequired
   }),
   editorOptionsVisible: PropTypes.bool.isRequired,
   showEditorOptions: PropTypes.func.isRequired,
@@ -223,7 +246,8 @@ Editor.propTypes = {
   isPlaying: PropTypes.bool.isRequired,
   theme: PropTypes.string.isRequired,
   unsavedChanges: PropTypes.bool.isRequired,
-  projectSavedTime: PropTypes.string.isRequired
+  projectSavedTime: PropTypes.string.isRequired,
+  files: PropTypes.array.isRequired
 };
 
 export default Editor;