process: add 'worker' event

doc/api/process.md

@@ -457,6 +457,15 @@ of the custom deprecation.
 The `*-deprecation` command-line flags only affect warnings that use the name
 `'DeprecationWarning'`.
 
+### Event: `'worker'`
+<!-- YAML
+added: REPLACEME
+-->
+
+* `worker` {Worker} The {Worker} that was created.
+
+The `'worker'` event is emitted after a new {Worker} thread has been created.
+
 #### Emitting custom warnings
 
 See the [`process.emitWarning()`][process_emit_warning] method for issuing

lib/internal/worker.js

@@ -266,6 +266,8 @@ class Worker extends EventEmitter {
     };
     // Actually start the new thread now that everything is in place.
     this[kHandle].startThread();
+
+    process.nextTick(() => process.emit('worker', this));
   }
 
   [kOnExit](code, customErr, customErrReason) {

test/parallel/test-worker-event.js

@@ -0,0 +1,14 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const {
+  Worker,
+  threadId: parentThreadId,
+} = require('worker_threads');
+
+process.on('worker', common.mustCall(({ threadId }) => {
+  assert.strictEqual(threadId, parentThreadId + 1);
+}));
+
+new Worker('', { eval: true });

tools/doc/type-parser.js

@@ -223,6 +223,7 @@ const customTypesMap = {
   'vm.SourceTextModule': 'vm.html#vm_class_vm_sourcetextmodule',
 
   'MessagePort': 'worker_threads.html#worker_threads_class_messageport',
+  'Worker': 'worker_threads.html#worker_threads_class_worker',
 
   'X509Certificate': 'crypto.html#crypto_class_x509certificate',