async-timeout-js/asynctimeout.js

/// An async wrapper around `setTimeout()` and `setInterval()`. 
///
/// # `setTimeout()`
/// `await (new AsyncTimeout(() => "value", 100)).timeout() /* === "value" */` is `setTimeout(()=> "value", 100)` promisified.
///
/// # `setInterval()`
/// `for await (const value of new AsyncTimeout(() => "value", 100)).interval()) { /* value === "value" */ }` is `setInterval(()=> "value", 100)` promisified.
/// This is an infinite iterator. To cancel the interval, simply break out of the `for await` loop.
///
/// # Parameters
/// * `thing` - The function to call after the timeout/interval. The result of the promise (or the yield for `interval()`) is the result of this function call. If the funtion throws, then the rejection of the promise will be that error thrown.
/// * `interval` - The time to wait for the timeout or interval
///
/// # Examples
/// See `examples` below.
function AsyncTimeout(thing, interval)
{
	this.timeout = () => new Promise((resolve, reject) => {
		setTimeout(() => {
			try {
				resolve(thing());
			} catch(e) { reject(e); }
		}, interval);
	});
	this.interval = async function*() => {
		while(true) {
			yield await new Promise((resolve, reject) => {
				setTimeout(() => {
					try { resolve(thing()); } catch(e) { reject(e); }
				}, interval);
			});
		}
	};
}

const example = async (_timeout) => {
	_timeout = _timeout || 100;

	// Wait 100 then alert "hi"
	alert(await (new AsyncTimeout(() => "hi", _timeout)).timeout());

	// Continuously wait 100 then alert "hi"
	for await (const value of new AsyncTimeout(() => "hi forever", _timeout).interval()) { alert(value); }
};