import mitt from 'mitt'; const emitter = mitt(); function once(event, handler) { const wrapper = (...args) => { emitter.off(event, wrapper); handler(...args); }; emitter.on(event, wrapper); } export default { // Vue 2-style alias $on: emitter.on, $off: emitter.off, $emit: emitter.emit, $once: once, // Plain methods used by PS4 branch on: emitter.on, off: emitter.off, emit: emitter.emit, once, };