Queue Emitter

Emit events in series, rather than in parallel Functions can be asynchronous (next function will start after the first function's Promise resolves) Functions can halt the emitter

Note: values returned by the functions are ignored. The arguments passed are the ones passed into the emit function

Usage

2 Functions, One asynchronous

const emitter = new QueueEmitter();

function callback1(obj) {
	obj.key1 = 'val1';
}

async function callback2(obj) {
	return new Promise(async function(resolve, reject) {
		setTimeout(() => {
			obj.key2 = 'val2';
			resolve();
		}, 100);
	});
}

emitter.on('eventname', callback1);
emitter.on('eventname', callback2);

let obj = {
	key0: 'val0'
};

await emitter.emit('eventname', obj);

if(obj.key0 !== 'val0' || obj.key1 !== 'val1' || obj.key2 !== 'val2')
	throw new Error('values not set properly');

Reject in one callback

const emitter = new QueueEmitter();

function callback1(obj) {
	obj.key1 = 'val1';
}

async function callback2(obj) {
	throw new Error('some_error')
}

emitter.on('eventname', callback1);
emitter.on('eventname', callback2);

try {
	await emitter.emit('eventname', {});
}
catch(error) {
	if(error.message !== 'some_error')
		throw error;
}

Useage with 'once'

const emitter = new QueueEmitter();

let triggered = false;
function callback1(obj) {
	if(triggered)
		throw new Error('previously_triggered');
	triggered = true;
}

emitter.once('eventname', callback1);

await emitter.emit('eventname', {});
await emitter.emit('eventname', {});