isleward/src/server/misc/events.js

module.exports = {
	events: {},

	//The only supported option right now is isAsync: boolean
	on: function (event, callback, options) {
		let list = this.events[event] || (this.events[event] = []);
		list.push({ callback, ...options });

		return callback;
	},

	off: function (event, callback) {
		let list = this.events[event] || [];
		let lLen = list.length;
		for (let i = 0; i < lLen; i++) {
			const { callback: lCallback } = list[i];

			if (lCallback === callback) {
				list.splice(i, 1);
				i--;
				lLen--;
			}
		}

		if (lLen === 0)
			delete this.events[event];
	},

	emit: async function (event) {
		let args = [].slice.call(arguments, 1);

		let list = this.events[event];
		if (!list)
			return;

		for (let l of list) {
			const { isAsync, callback } = l;

			if (isAsync)
				await callback.apply(null, args);
			else
				callback.apply(null, args);
		}
	}
};