问题描述
我已经研究了关于通过forEach循环使用async/await的几个问题，但似乎没有什么能解决我的用户情况...如何才能使下面的代码正常工作?现在，我收到以下错误:
I've looked at several questions on using async/await with a forEach loop but nothing seems to cover my user case... How can I get the code below to work? Right now I'm getting the following error:
这是代码:
export const fetchUserBookmarks = ( bookmarksIDs ) => async ( dispatch, getState, api ) => {
dispatch({
type: 'IS_FETCHING_BOOKMARKS'
});
try {
bookmarks = [];
bookmarksIDs.forEach( bookmarkID => {
const bookmark = await api.get( selectedPostByIdEP + bookmarkID );
bookmarks.push( bookmark );
});
dispatch({
type: 'HAS_FETCHED_BOOKMARKS',
payload: bookmarks
});
} catch( error ) {
dispatch({
type: 'FAILED_FETCHING_BOOKMARKS',
payload: error
});
}
}
推荐答案
首先，要使用await，应将函数声明为async.您是通过外部函数完成的，而不是内部函数完成的.
First, To use await you should declare the function as async. You have done so with the outer function but not with the inner function.
更改将如下所示:
bookmarksIDs.forEach(async bookmarkID => {
第二，，您可能想要并行运行这些api调用.
Second, what you probably want is to run those api calls in parallel.
您可以将forEach替换为map调用，然后等待所有产生的诺言.
You can replace forEach with a map call and await all the resulting promises together.
为此，您的代码应如下所示:
To do that your code should look something like this:
const bookmarks = await Promise.all(
bookmarksIDs.map(bookmarkID =>
api.get( selectedPostByIdEP + bookmarkID )
)
);
-
如果在其他任何地方未声明bookmarks，似乎会导致问题.使用const或let应该可以解决该问题.
It seems that if bookmarks is not declared anywhere else it causes a problem. using const or let should solve that problem.
这篇关于如何在Javascript中的forEach循环中使用异步/等待语法?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！