4.2 KiB
4.2 KiB
id | title | challengeType | isRequired |
---|---|---|---|
5a24c314108439a4d403615b | Copy an Object with Object.assign | 6 | false |
Description
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
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.
Tests
tests:
- text: The Redux store should exist and initialize with a state that is equivalent to the <code>defaultState</code> object declared on line 1.
testString: 'assert((function() { const expectedState = { user: ''CamperBot'', status: ''offline'', friends: ''732,982'', community: ''freeCodeCamp'' }; const initialState = store.getState(); return DeepEqual(expectedState, initialState); })(), ''The Redux store should exist and initialize with a state that is equivalent to the <code>defaultState</code> object declared on line 1.'');'
- text: <code>wakeUp</code> and <code>immutableReducer</code> both should be functions.
testString: assert(typeof wakeUp === 'function' && typeof immutableReducer === 'function', '<code>wakeUp</code> and <code>immutableReducer</code> both should be functions.');
- text: Dispatching an action of type <code>ONLINE</code> should update the property <code>status</code> in state to <code>online</code> and should NOT mutate state.
testString: '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); })(), ''Dispatching an action of type <code>ONLINE</code> should update the property <code>status</code> in state to <code>online</code> and should NOT mutate state.'');'
- text: <code>Object.assign</code> should be used to return new state.
testString: getUserInput => assert(getUserInput('index').includes('Object.assign'), '<code>Object.assign</code> should be used to return new state.');
Challenge Seed
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);
Solution
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);