EventTarget: EventTarget() constructor

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since September 2020.

Note: This feature is available in Web Workers.

The EventTarget() constructor creates a new EventTarget object instance.

Note: It is fairly rare to explicitly call this constructor. Most of the time, this constructor is used inside the constructor of an object extending the EventTarget interface, using the super keyword.

Syntax

new EventTarget()

Parameters

None.

Return value

A new instance of the EventTarget object.

Examples

Implementing a counter

This example implements a Counter class, with increment() and decrement() methods. It fires a custom "valuechange" event when either of these methods is called.

HTML

html
<button id="dec" aria-label="Decrement">-</button>
<span id="currentValue">0</span>
<button id="inc" aria-label="Increment">+</button>

JavaScript

js
class Counter extends EventTarget {
  constructor(initialValue = 0) {
    super();
    this.value = initialValue;
  }

  #emitChangeEvent() {
    this.dispatchEvent(new CustomEvent("valuechange", { detail: this.value }));
  }

  increment() {
    this.value++;
    this.#emitChangeEvent();
  }

  decrement() {
    this.value--;
    this.#emitChangeEvent();
  }
}

const initialValue = 0;
const counter = new Counter(initialValue);
document.querySelector("#currentValue").innerText = initialValue;

counter.addEventListener("valuechange", (event) => {
  document.querySelector("#currentValue").innerText = event.detail;
});

document.querySelector("#inc").addEventListener("click", () => {
  counter.increment();
});

document.querySelector("#dec").addEventListener("click", () => {
  counter.decrement();
});