2.4 KiB
2.4 KiB
id | title | challengeType | forumTopicId | dashedName |
---|---|---|---|---|
5a24c314108439a4d403615a | 从数组中删除项目 | 6 | 301447 | remove-an-item-from-an-array |
--description--
是时候练习从数组中删除项目了。扩展运算符也可以在这里使用。其他有用的JavaScript方法包括slice()
和concat()
。
--instructions--
reducer 和 action creator 被修改为根据项目的索引从数组中删除一个项目。完成编写 reducer 以便返回一个新的状态数组,并删除特定索引处的项目。
--hints--
Redux store 应该存在并初始化一个[0,1,2,3,4,5]
的状态。
assert(
(function () {
const initialState = store.getState();
return (
Array.isArray(initialState) === true &&
DeepEqual(initialState, [0, 1, 2, 3, 4, 5])
);
})()
);
removeItem
和immutableReducer
都应该是一个函数。
assert(
typeof removeItem === 'function' && typeof immutableReducer === 'function'
);
dispatch removeItem
action creator 应该从 state 中删除项目,不应该改变 state。
assert(
(function () {
const initialState = store.getState();
const isFrozen = DeepFreeze(initialState);
store.dispatch(removeItem(3));
const state_1 = store.getState();
store.dispatch(removeItem(2));
const state_2 = store.getState();
store.dispatch(removeItem(0));
store.dispatch(removeItem(0));
store.dispatch(removeItem(0));
const state_3 = store.getState();
return (
isFrozen &&
DeepEqual(state_1, [0, 1, 2, 4, 5]) &&
DeepEqual(state_2, [0, 1, 4, 5]) &&
DeepEqual(state_3, [5])
);
})()
);
--seed--
--seed-contents--
const immutableReducer = (state = [0,1,2,3,4,5], action) => {
switch(action.type) {
case 'REMOVE_ITEM':
// Don't mutate state here or the tests will fail
return
default:
return state;
}
};
const removeItem = (index) => {
return {
type: 'REMOVE_ITEM',
index
}
}
const store = Redux.createStore(immutableReducer);
--solutions--
const immutableReducer = (state = [0,1,2,3,4,5], action) => {
switch(action.type) {
case 'REMOVE_ITEM':
return [
...state.slice(0, action.index),
...state.slice(action.index + 1)
];
default:
return state;
}
};
const removeItem = (index) => {
return {
type: 'REMOVE_ITEM',
index
}
}
const store = Redux.createStore(immutableReducer);