Solution

src/transformState.js

@@ -5,7 +5,33 @@
  * @param {Object[]} actions
  */
 function transformState(state, actions) {
-  // write code here
+  const add = 'addProperties';
+  const remove = 'removeProperties';
+  const clear = 'clear';
+
+  for (const action of actions) {
+    switch (action.type) {
+      case add:
+        Object.assign(state, action.extraData);
+        break;
+
+      case remove:
+        for (const removeKey of action.keysToRemove) {
+          if (removeKey in state) {
+            delete state[removeKey];
+          };
+        };
+        break;
+
+      case clear:
+        for (const clearKey in state) {
+          delete state[clearKey];
+        };
+        break;
+    };
+  };
+
+  return state;
 }
 
 module.exports = transformState;