@nevware21 ts-async

Promise support implementations and helpers for TypeScript built for minification

Description

This library provides Promise implementations (synchronous, idle, asynchronous and native), helpers and aliases built and tested using TypeScript. Apart from providing idle and synchronous implementations the primary focus is on supporting the creation of production code that can be better minified (resulting in a smaller runtime payload).

Provided implementations:

• Idle processing
• Synchronous processing
• Asynchronous processing
• Native runtime wrapper

The primary helpers are

• createPromise - Uses the current promise implementation set via setCreatePromiseImpl (defaults to createNativePromise)
• createNativePromise - This is a wrapper around the runtime Promise class that adds a status property, so this is effectivly the same as new Promise(...) but as a non-namespaced function it can be heavily minified to something like a(...)
• createAsyncPromise - Implements the Promise contract and uses timeouts (defaults to 0ms, but can also be provided) to process any chained promises (of any type)
• createSyncPromise - Also implements the Promise contract but will immediately execute any chained promises at the point of the original promise getting resolved or rejected, or if already resolved, rejected then at the point of registering the then, catch or finally
• createIdlePromise - Implements the Promise contract and will process any chained promises using the available requestIdleCallback (with no timeout by default - but can also be changes by setDetaultIdlePromiseTimeout). And when requestIdleCallback is not supported this will default to using a timeout via the scheduleIdleCallback from @nevware21/ts-utils
• doAwait - Helper which handles await "handling" via callback functions to avoid the TypeScript boilerplate code that is added for multiple branches. Has 3 callback options for resolved, rejected and finally cases all are optional.
• doAwaitResponse - Helper which handles await "handling" via a single callback where resolved and rejected cases are handled by the same callback, this receives an AwaitResponse object that provides the value or reason and a flag indicating whether the Promise was rejected)
• doFinally - Helper to provide finally handling for any promise using a callback implementation, analogous to using try / finally around an await function or using the finally on the promise directly

All promise implementations are validated using TypeScript with async / await and the internal helper functions doAwait, doFinally and doAwaitResponse helpers. Usage of the doAwait is recommended as this will avoids the additional boiler plate code that is added by TypeScript when handling the branches in an async / await functions, this does of course mean that your calling functions will also need to handle this async operations via callbacks rather than just causing the code path to "halt" at the await and can therefore may be a little more complex (depending on your implementation), however, you are not restricted to only using await or doAwait they can be used together.

Also of note is that all implementations will "emit/dispatch" the unhandled promise rejections event (if supported by the runtime) using the standard runtime mechanisms. So any existing handlers for native (new Promise) unhandled rejections will also receive them from the idle, sync and async implementations. The only exception to this is when the runtime (like IE) doesn't support this event in those cases "if" an onunhandledrejection function is registered it will be called or failing that it will logged to the console (if possible).

The provided polyfill wrapper is build around the asynchronous promise implementation which is tested and validated against the standard native (Promise()) implementations for node, browser and web-worker to ensure compatibility.

Test Environments

• Node (12, 14, 16, 18)
• Browser (Chromium - headless)
• Web Worker (Chromium - headless)

Documentation and details

See the documentation generated from source code via typedoc for a full list and details of all of the available types, functions and interfaces.

Quickstart

Install the npm packare: npm install @nevware21/ts-async --save

And then just import the helpers and use them.

Simple Examples

import { createPromise } from "@nevware21/ts-async";
import { scheduleTimeout } from "@nevware21/ts-utils";

const myPromise = createPromise((resolve, reject) => {
    scheduleTimeout(() => {
        resolve("foo");
    }, 300);
});

myPromise
  .then(handleFulfilledA, handleRejectedA)
  .then(handleFulfilledB, handleRejectedB)
  .then(handleFulfilledC, handleRejectedC)
  .catch(handleRejectedAny);

// Create a new promise that resolves with an inner promise that will auto resolve after 1 second
createPromise((resolveOuter) => {
  resolveOuter(
    createPromise((resolveInner) => {
      scheduleTimeout(resolveInner, 1000);
    })
  );
});

doAwait(myPromise, (result) => {
    // Handle the result this would normally be
    // let result = await myPromise;
}, (reason) => {
    // Handle cases when the `myPromise` is rejected
    // Using await you would handle this via try / catch
});

While the examples above are using the createPromise you can directly use the createSyncPromise, createAsyncPromise, createIdlePromise or createNativePromise, you can also mix and match them (ie. they don't all have to be the same implementation). The createPromise alias is provided to enable switching the underlying Promise implementation without changing any of your code.

Release Notes

• Releases
• Changelist Notes

Browser Support

General support is currently set to ES5 supported runtimes higher.

Internal polyfills are used to backfill ES5 functionality which is not provided by older browsers.

Latest ✔	Latest ✔	9+ ✔	Latest ✔	Latest ✔

Note: A PolyFill PolyPromise provides the standard promise implementations for IE and ES5+ environments.

Contributing

Read our contributing guide to learn about our development process, how to propose bugfixes and improvements, and how to build and test your changes.