3.6 KiB
3.6 KiB
id | title | challengeType | isRequired | videoUrl | localeTitle |
---|---|---|---|---|---|
5a24c314108439a4d403615b | Copy an Object with Object.assign | 6 | false | 使用Object.assign复制对象 |
Description
object
时,有一些方法可以帮助强制执行状态不变性。处理对象的有用工具是Object.assign()
实用程序。 Object.assign()
接受目标对象和源对象,并将源对象中的属性映射到目标对象。任何匹配的属性都会被源对象中的属性覆盖。此行为通常用于通过将空对象作为第一个参数传递,然后传递要复制的对象来生成对象的浅副本。这是一个例子: const newObject = Object.assign({}, obj1, obj2);
这将newObject
创建为一个新object
,其中包含当前存在于obj1
和obj2
中的属性。 Instructions
state
的object
。编辑代码以返回类型为ONLINE
操作的新state
对象,该status
属性将status
属性设置为online
字符串。尝试使用Object.assign()
来完成挑战。 Tests
tests:
- text: Redux存储应该存在并使用等效于第1行声明的<code>defaultState</code>对象的状态进行初始化。
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>和<code>immutableReducer</code>都应该是函数。
testString: 'assert(typeof wakeUp === "function" && typeof immutableReducer === "function", "<code>wakeUp</code> and <code>immutableReducer</code> both should be functions.");'
- text: 调度<code>ONLINE</code>类型的操作应该将<code>status</code>中的属性<code>status</code>更新为<code>online</code>并且不应该改变状态。
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>应该用于返回新状态。
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
// solution required