freeCodeCamp/curriculum/challenges/english/03-front-end-development-libraries/redux/copy-an-object-with-object.assign.md

id, title, challengeType, forumTopicId, dashedName

id	title	challengeType	forumTopicId	dashedName
5a24c314108439a4d403615b	Copy an Object with Object.assign	6	301437	copy-an-object-with-object-assign

--description--

The last several challenges worked with arrays, but there are ways to help enforce state immutability when state is an object, too. A useful tool for handling objects is the Object.assign() utility. Object.assign() takes a target object and source objects and maps properties from the source objects to the target object. Any matching properties are overwritten by properties in the source objects. This behavior is commonly used to make shallow copies of objects by passing an empty object as the first argument followed by the object(s) you want to copy. Here's an example:

const newObject = Object.assign({}, obj1, obj2);

This creates newObject as a new object, which contains the properties that currently exist in obj1 and obj2.

--instructions--

The Redux state and actions were modified to handle an object for the state. Edit the code to return a new state object for actions with type ONLINE, which set the status property to the string online. Try to use Object.assign() to complete the challenge.

--hints--

The Redux store should exist and initialize with a state that is equivalent to the defaultState object declared on line 1.

assert(
  (function () {
    const expectedState = {
      user: 'CamperBot',
      status: 'offline',
      friends: '732,982',
      community: 'freeCodeCamp'
    };
    const initialState = store.getState();
    return DeepEqual(expectedState, initialState);
  })()
);

wakeUp and immutableReducer both should be functions.

assert(typeof wakeUp === 'function' && typeof immutableReducer === 'function');

Dispatching an action of type ONLINE should update the property status in state to online and should NOT mutate state.

assert(
  (function () {
    const initialState = store.getState();
    const isFrozen = DeepFreeze(initialState);
    store.dispatch({ type: 'ONLINE' });
    const finalState = store.getState();
    const expectedState = {
      user: 'CamperBot',
      status: 'online',
      friends: '732,982',
      community: 'freeCodeCamp'
    };
    return isFrozen && DeepEqual(finalState, expectedState);
  })()
);

Object.assign should be used to return new state.

(getUserInput) => assert(getUserInput('index').includes('Object.assign'));

--seed--

--seed-contents--

const defaultState = {
  user: 'CamperBot',
  status: 'offline',
  friends: '732,982',
  community: 'freeCodeCamp'
};

const immutableReducer = (state = defaultState, action) => {
  switch(action.type) {
    case 'ONLINE':
      // Don't mutate state here or the tests will fail
      return
    default:
      return state;
  }
};

const wakeUp = () => {
  return {
    type: 'ONLINE'
  }
};

const store = Redux.createStore(immutableReducer);

--solutions--

const defaultState = {
  user: 'CamperBot',
  status: 'offline',
  friends: '732,982',
  community: 'freeCodeCamp'
};

const immutableReducer = (state = defaultState, action) => {
  switch(action.type) {
    case 'ONLINE':
      return Object.assign({}, state, {
        status: 'online'
      });
    default:
      return state;
  }
};

const wakeUp = () => {
  return {
    type: 'ONLINE'
  }
};

const store = Redux.createStore(immutableReducer);