jQuery 2 - TypeScript async/await Adapter

Replaces TypeScript's generated async/await support code so jQuery 2's crappy JQueryPromise can be used with async/await.

Usage

This only works in the browser with jQuery 2 and TypeScript >= 2.1 set to output ES3 or ES5 JavaScript. Include lib/index.js so that it's run before any code using the await keyword.

Technical Details

TypeScript emits a global __awaiter method for async/await code. It assumes the existence of a Promise constructor and other sane standards. This library replaces it with a similar versions that instead uses $.Deferred().promise().

Caveats

You should move to jQuery 3. It has standards-compliant Promises. This library should only be used as a polyfill while your team works on the update.

jQuery 2's .then is synchronous by default but can by asynchronous. Standards-compliant Promise implementations are always asynchronous. Don't structure your code assuming .then callbacks are run synchronously.

Because .then is synchronous, if an error is thrown synchronously in a JQueryPromise, any subsequent code (including awaits) will not be run. That means you can't use await within try blocks on this adapter. Put the risky logic in a non-async function instead.

Development

This requres NodeJS >= 6.0.

1. Clone the repository with git clone https://github.com/joshuakgoldberg/jquery-2-typescript-async-await-adapter
2. Install tools with npm install && npm install -g gulp
3. Build the test case with gulp tsc
4. Run the test on the command-line with gulp test or in the browser by opening test/index.html