Binding event listeners

loader.js

function registerComponent( { template, style, name, listeners } ) { // 1
	class UnityComponent extends HTMLElement {
		connectedCallback() {
			this._upcast();
			this._attachListeners(); // 2
		}

		[…]

		_attachListeners() {
			Object.entries( listeners ).forEach( ( [ event, listener ] ) => { // 3
				this.addEventListener( event, listener, false ); // 4
			} );
		}
	}

	return customElements.define( name, UnityComponent );
}