Prevent crashes when working with ES2015 symbols

demo/src/js/DemoApp.jsx

@@ -109,6 +109,9 @@ class DemoApp extends React.Component {
             <Button onClick={this.props.addFunction} style={styles.button}>
               Add Function
             </Button>
+            <Button onClick={this.props.addSymbol} style={styles.button}>
+              Add Symbol
+            </Button>
           </div>
         </div>
         <div style={styles.links}>
@@ -155,6 +158,7 @@ export default connect(
       type: 'HUGE_PAYLOAD',
       payload: Array.from({ length: 10000 }).map((_, i) => i)
     }),
-    addFunction: () => ({ type: 'ADD_FUNCTION' })
+    addFunction: () => ({ type: 'ADD_FUNCTION' }),
+    addSymbol: () => ({ type: 'ADD_SYMBOL' })
   }
 )(DemoApp);

demo/src/js/reducers.js

@@ -90,5 +90,7 @@ export default combineReducers({
       str => str + '!'
     ) : state,
   addFunction: (state=null, action) => action.type === 'ADD_FUNCTION' ?
-    { f: FUNC } : state
+    { f: FUNC } : state,
+  addSymbol: (state=null, action) => action.type === 'ADD_SYMBOL' ?
+    { s: Symbol('symbol') } : state
 });

package.json

@@ -65,7 +65,7 @@
     "babel-runtime": "^6.3.19",
     "dateformat": "^1.0.12",
     "immutable": "^3.7.6",
-    "javascript-stringify": "^1.0.2",
+    "javascript-stringify": "^1.1.0",
     "jsondiffpatch": "^0.1.41",
     "jss": "^3.3.0",
     "jss-nested": "^1.0.2",

src/ActionPreview.jsx

@@ -30,6 +30,8 @@ function getItemString(createTheme, type, data) {
       return 'fn';
     } else if (typeof val === 'string') {
       return `"${val.substr(0, 10) + (val.length > 10 ? '…' : '')}"`
+    } else if (typeof val === 'symbol') {
+      return 'symbol'
     } else {
       return val;
     }