How does the async/await syntax work in TypeScript?

The key is to use an ES6 Promise or something that implements the PromiseLike and PromiseConstructorLike interfaces found in lib.d.ts (Read more). A jQuery promise does not implement these interfaces so it won't work with that.

Here's a simple example using an ES6 promise:

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 await statement needs to be within an async function 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 here and see here for TypeScript details.

Please note that you need to target ES6 in Typescript 1.7 to use async/await. With lower versions, Visual Studio outputs

TS1308 'await' expression is only allowed within an async function.

and

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