Solution

package.json

@@ -16,7 +16,7 @@
   "license": "GPL-3.0",
   "devDependencies": {
     "@mate-academy/eslint-config": "*",
-    "@mate-academy/scripts": "^0.3.5",
+    "@mate-academy/scripts": "^1.2.8",
     "eslint": "^5.16.0",
     "eslint-plugin-jest": "^22.4.1",
     "eslint-plugin-node": "^8.0.1",

src/transformState.js

@@ -5,7 +5,42 @@
  * @param {Object[]} actions
  */
 function transformState(state, actions) {
-  // write code here
+  for (const action of actions) {
+    const { type } = action;
+
+    switch (type) {
+      case 'addProperties': {
+        const { extraData } = action;
+
+        for (const key in extraData) {
+          state[key] = extraData[key];
+        }
+        break;
+      }
+
+      case 'removeProperties': {
+        const { keysToRemove } = action;
+
+        for (const key of keysToRemove) {
+          if (state.hasOwnProperty(key)) {
+            delete state[key];
+          }
+        }
+        break;
+      }
+
+      case 'clear': {
+        for (const key in state) {
+          delete state[key];
+        }
+        break;
+      }
+
+      default: {
+        throw new Error(`Unknown action type: ${type}`);
+      }
+    }
+  }
 }
 
 module.exports = transformState;