add task solution

src/transformState.js

@@ -5,7 +5,30 @@
  * @param {Object[]} actions
  */
 function transformState(state, actions) {
-  // write code here
+  for (const action of actions) {
+    switch (action.type) {
+      case 'addProperties':
+        Object.assign(state, action.extraData);
+        break;
+
+      case 'removeProperties':
+        action.keysToRemove.forEach((key) => {
+          if (state.hasOwnProperty(key)) {
+            delete state[key];
+          }
+        });
+        break;
+
+      case 'clear':
+        Object.keys(state).forEach((key) => delete state[key]);
+        break;
+
+      default:
+        throw Error('Invalid input.');
+    }
+  }
+
+  return state;
 }
 
 module.exports = transformState;