如何从承诺中返回.都是打字的吗?

Question

我有一个url列表，我需要取回所有的，所以我使用取回，然后承诺。但是，我不知道如何返回承诺的结果。

let photos_info = [];
function get_photos(urls) {
var promises = urls.map((url) => fetch(url).then((y) => y.json()));
Promise.all(promises).then((results) => {

console.log("results:", results);
photos_info = [...results];
console.log("photos_info:", photos_info );
});
return photos_info ;
}
const list_of_photos = get_photos(urls);
console.log("result of the function", list_of_photos);

为什么list_of_photos返回一个空列表，而当在函数中打印photos_info时，它返回一个列表。

Answer 1

这是因为你的承诺。所有异步运行

因此return photos_info将在得到未定义结果的响应之前运行。

改为:

let photos_info = [];
async function get_photos(urls) {
var promises = urls.map((url) => fetch(url).then((y) => y.json()));
await Promise.all(promises).then((results) => {

console.log("results:", results);
photos_info = [...results];
console.log("photos_info:", photos_info );
});
return photos_info ;
}
const list_of_photos = get_photos(urls);
console.log("result of the function", list_of_photos);

您在控制台日志中获得响应的原因是它在then块中，该块仅在承诺响应成功后运行(这也是异步的)