events: initial implementation of experimental EventTarget

See documentation changes for details

Signed-off-by: James M Snell <jasnell@gmail.com>

benchmark/events/eventtarget.js

@@ -0,0 +1,24 @@
+'use strict';
+const common = require('../common.js');
+
+const bench = common.createBenchmark(main, {
+  n: [2e7],
+  listeners: [1, 5, 10]
+}, { flags: ['--expose-internals'] });
+
+function main({ n, listeners }) {
+  const { EventTarget, Event } = require('internal/event_target');
+  const target = new EventTarget();
+
+  for (let n = 0; n < listeners; n++)
+    target.addEventListener('foo', () => {});
+
+  const event = new Event('foo');
+
+  bench.start();
+  for (let i = 0; i < n; i++) {
+    target.dispatchEvent(event);
+  }
+  bench.end(n);
+
+}

doc/api/errors.md

@@ -903,6 +903,11 @@ Encoding provided to `TextDecoder()` API was not one of the
 
 `--print` cannot be used with ESM input.
 
+<a id="ERR_EVENT_RECURSION"></a>
+### `ERR_EVENT_RECURSION`
+
+Thrown when an attempt is made to recursively dispatch an event on `EventTarget`.
+
 <a id="ERR_EXECUTION_ENVIRONMENT_NOT_AVAILABLE"></a>
 ### `ERR_EXECUTION_ENVIRONMENT_NOT_AVAILABLE`