在定位Safari时如何在TypeScript（angular2）中使用await / async？

Question

I have added some code similar to the following in my project:

async fun2(): Promise<string> {
  let token: string = null;

  await this.auth.getToken().then(newToken => {
    token = newToken;
  });

  return token;
}

However, when it is compiling, I get the warning:

Async functions are only available when targeting ECMAScript 2015 or higher.

When I try to run the project in Chrome it works fine, however in Safari I get an error on __awaiter function.

proj.prototype.fun2 = function () {
        return __awaiter(this, void 0, Promise, function * () {
            var token = null;

What do I need to do to use async/await in Safari with Typescript?

Answer 1

In your tsconfig.json , you need to set "target": "es6" in the compilerOptions section. Note that only Safari v10.0 is fully ES6 compliant, so you need to be on that version. Your code will likely not run in other browsers, as their ES6/ES2015 support is not yet complete.

Promise is part of ES2015, so nothing needs to be done if you switch to the es6 target.

UPDATE : As of TypeScript 2.1, you can use async/await when targeting ES5.

Answer 2

1) Make sure you have TypeScript 2.1. Earlier versions don't fully support async await when targeting ES5.

2) To make Promise valid in ES5, follow the instructions of the accepted answer of this question: TypeScript Promise TS2304 TS2529