What is the output of the following? “`js class EventEmitter { #handlers = {}; on(event, handler) { (this.#handlers[event] ??= []).push(handler); } emit(event, data) { this.#handlers[event]?.forEach(h => h(data)); } } const ee = new EventEmitter(); ee.on(‘test’, v => console.log(v * 2)); ee.emit(‘test’, 5); ee.emit(‘missing’, 5); “`

Question

JavaScript Professional — Medium

What is the output of the following? “`js class EventEmitter { #handlers = {}; on(event, handler) { (this.#handlers[event] ??= []).push(handler); } emit(event, data) { this.#handlers[event]?.forEach(h => h(data)); } } const ee = new EventEmitter(); ee.on(‘test’, v => console.log(v * 2)); ee.emit(‘test’, 5); ee.emit(‘missing’, 5); “`

Accepted Answer

The output of the code will be 10 then nothing. The event 'test' is emitted with the value 5, which triggers the handler to log 5 * 2 = 10. However, since there is no handler for the 'missing' event, nothing will be output.