Solution to spread operators in Redux challange (#34268)

guide/english/certifications/front-end-libraries/redux/use-the-spread-operator-on-arrays/index.md

@@ -2,9 +2,30 @@
 title: Use the Spread Operator on Arrays
 ---
 ## Use the Spread Operator on Arrays
-
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-
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+
+
+## Solution
+
+```javascript
+const immutableReducer = (state = ['Do not mutate state!'], action) => {
+  switch(action.type) {
+    case 'ADD_TO_DO':
+      // don't mutate state here or the tests will fail
+      let arr = [...state];
+      arr.push(action.todo);
+      return arr;
+    default:
+      return state;
+  }
+};
+
+const addToDo = (todo) => {
+  return {
+    type: 'ADD_TO_DO',
+    todo
+  }
+}
+
+const store = Redux.createStore(immutableReducer);
+```