typescript Async/Await ，简单示例（打字稿）
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Async/Await , simple example (typescript)
提问by Pranay Dutta
I am quite familiar with the async/await of c# and been using typescript for a year or so, can anyone please give a simple example explaining how it works on typescript?? Thanks in advance , looking forward to find some help and implement the same
我非常熟悉 c# 的 async/await 并且已经使用 typescript 一年左右了，谁能举一个简单的例子来解释它是如何在 typescript 上工作的？提前致谢，期待找到一些帮助并实现相同的
UPDATE
it would be very helpful if the example includes angular/jquery promise, as it will give a clear view of practical implementation
更新
如果示例包含 angular/jquery 承诺将非常有帮助，因为它将清楚地了解实际实现
回答by David Sherret
The key is to use an ES6 Promiseor something that implements the PromiseLikeand PromiseConstructorLikeinterfaces found in lib.d.ts(Read more). A jQuery promise does not implementthese interfaces so it won't work with that.
关键是使用ES6 Promise或实现lib.d.ts 中的PromiseLike和PromiseConstructorLike接口的东西（阅读更多）。jQuery 承诺没有实现这些接口，因此它不会与这些接口一起工作。
Here's a simple example using an ES6 promise:
这是一个使用 ES6 承诺的简单示例：
function getStringFromWebServerAsync(url: string) {
return new Promise<string>((resolve, reject) => {
// note: could be written `$.get(url).done(resolve).fail(reject);`,
// but I expanded it out for clarity
$.get(url).done((data) => {
resolve(data);
}).fail((err) => {
reject(err);
});
});
}
async function asyncExample() {
try {
const data = await getStringFromWebServerAsync("http://localhost/GetAString");
console.log(data);
}
catch (err) {
console.log(err);
}
}
asyncExample();
Note that any code containing an awaitstatement needs to be within an asyncfunction and so I have wrapped the code in one. That said, an upcoming proposal adds "top-level await", which will be available in TypeScript 3.8. Read more hereand see here for TypeScript details.
请注意，任何包含await语句的代码都需要在一个async函数中，因此我将这些代码合二为一。也就是说，即将到来的提案添加了“顶级等待”，它将在 TypeScript 3.8 中可用。在此处阅读更多信息并在此处查看 TypeScript 详细信息。
回答by Zartag
Please note that you need to target ES6 in Typescript 1.7 to use async/await. With lower versions, Visual Studio outputs
请注意，您需要在 Typescript 1.7 中以 ES6 为目标才能使用 async/await。对于较低版本，Visual Studio 输出
TS1308 'await' expression is only allowed within an async function.
and
和
TS1311 Async functions are only available when targeting ECMAScript 6 and higher.
For more information see e.g. http://blogs.msdn.com/b/typescript/archive/2015/11/03/what-about-async-await.aspx
有关更多信息，请参见例如http://blogs.msdn.com/b/typescript/archive/2015/11/03/what-about-async-await.aspx
