Repository: nodejs/node
Pull request: worker: update code examples for `node:worker_threads` module

<!--
Before submitting a pull request, please read:

- the CONTRIBUTING guide at https://github.com/nodejs/node/blob/HEAD/CONTRIBUTING.md
- the commit message formatting guidelines at
  https://github.com/nodejs/node/blob/HEAD/doc/contributing/pull-requests.md#commit-message-guidelines

For code changes:
1. Include tests for any bug fixes or new features.
2. Update documentation if relevant.
3. Ensure that `make -j4 test` (UNIX), or `vcbuild test` (Windows) passes.

If you believe this PR should be highlighted in the Node.js CHANGELOG
please add the `notable-change` label.

Developer's Certificate of Origin 1.1

By making a contribution to this project, I certify that:

(a) The contribution was created in whole or in part by me and I
    have the right to submit it under the open source license
    indicated in the file; or

(b) The contribution is based upon previous work that, to the best
    of my knowledge, is covered under an appropriate open source
    license and I have the right under that license to submit that
    work with modifications, whether created in whole or in part
    by me, under the same open source license (unless I am
    permitted to submit under a different license), as indicated
    in the file; or

(c) The contribution was provided directly to me by some other
    person who certified (a), (b) or (c) and I have not modified
    it.

(d) I understand and agree that this project and the contribution
    are public and that a record of the contribution (including all
    personal information I submit with it, including my sign-off) is
    maintained indefinitely and may be redistributed consistent with
    this project or the open source license(s) involved.
-->

- Missed one import.
- Use `.once` for one time events.
- ~Use `node:assert/strict` instead of `node:assert`.~

Changed files:
filename: doc/api/worker_threads.md
patch: @@ -47,8 +47,8 @@ export default function parseJSAsync(script) {
       workerData: script,
     });
     worker.on('message', resolve);
-    worker.on('error', reject);
-    worker.on('exit', (code) => {
+    worker.once('error', reject);
+    worker.once('exit', (code) => {
       if (code !== 0)
         reject(new Error(`Worker stopped with exit code ${code}`));
     });
@@ -73,8 +73,8 @@ if (isMainThread) {
         workerData: script,
       });
       worker.on('message', resolve);
-      worker.on('error', reject);
-      worker.on('exit', (code) => {
+      worker.once('error', reject);
+      worker.once('exit', (code) => {
         if (code !== 0)
           reject(new Error(`Worker stopped with exit code ${code}`));
       });
@@ -670,7 +670,7 @@ share read and write access to the same set of environment variables.
 import process from 'node:process';
 import { Worker, SHARE_ENV } from 'node:worker_threads';
 new Worker('process.env.SET_IN_WORKER = "foo"', { eval: true, env: SHARE_ENV })
-  .on('exit', () => {
+  .once('exit', () => {
     console.log(process.env.SET_IN_WORKER);  // Prints 'foo'.
   });
 ```
@@ -680,7 +680,7 @@ new Worker('process.env.SET_IN_WORKER = "foo"', { eval: true, env: SHARE_ENV })
 
 const { Worker, SHARE_ENV } = require('node:worker_threads');
 new Worker('process.env.SET_IN_WORKER = "foo"', { eval: true, env: SHARE_ENV })
-  .on('exit', () => {
+  .once('exit', () => {
     console.log(process.env.SET_IN_WORKER);  // Prints 'foo'.
   });
 ```
@@ -1110,7 +1110,7 @@ const { port1, port2 } = new MessageChannel();
 //   foobar
 //   closed!
 port2.on('message', (message) => console.log(message));
-port2.on('close', () => console.log('closed!'));
+port2.once('close', () => console.log('closed!'));
 
 port1.postMessage('foobar');
 port1.close();
@@ -1126,7 +1126,7 @@ const { port1, port2 } = new MessageChannel();
 //   foobar
 //   closed!
 port2.on('message', (message) => console.log(message));
-port2.on('close', () => console.log('closed!'));
+port2.once('close', () => console.log('closed!'));
 
 port1.postMessage('foobar');
 port1.close();