feat(core) Base class Emitter

lib/core/Emitter.js

@@ -0,0 +1,69 @@
+class Emitter {
+	#listeners;
+	constructor() {
+		this.#listeners = {};
+	}
+
+	/**
+	 * Registers a callback function for the specified event.
+	 *
+	 * @param {string} event - The name of the event.
+	 * @param {Function} callback - The callback function to be executed when the event is triggered.
+	 */
+	on(event, callback) {
+		if (!this.#listeners[event]) {
+			this.#listeners[event] = [];
+		}
+		this.#listeners[event].push(callback);
+	}
+
+	/**
+	 * Removes an event listener callback for the specified event.
+	 * If no callback is provided, removes all callbacks for the event.
+	 *
+	 * @param {string} event - The name of the event.
+	 * @param {Function} [callback] - The callback function to be removed.
+	 */
+	off(event, callback = undefined) {
+		if (typeof event != 'string') {
+			throw new TypeError('event must be a string');
+			return;
+		}
+
+		if (
+			!Array.isArray(this.#listeners[event]) ||
+			this.#listeners[event].length === 0
+		) {
+			throw new TypeError(
+				`listener for \`${event}\` is not an array or empty`
+			);
+		}
+
+		if (!callback) {
+			this.#listeners[event] = undefined;
+			return;
+		}
+
+		this.#listeners[event] = this.#listeners[event].filter(
+			(listener) => listener !== callback
+		);
+	}
+
+	/**
+	 * Emits an event and invokes all registered listeners for that event.
+	 *
+	 * @param {string} event - The name of the event to emit.
+	 * @param {...any} args - The arguments to pass to the event listeners.
+	 */
+	emit(event, ...args) {
+		if (!this.#listeners[event]) {
+			return;
+		}
+
+		for (const callback of this.#listeners[event]) {
+			callback(this, ...args);
+		}
+	}
+}
+
+export default Emitter;