doc: normalize JavaScript code block info strings

doc/api/fs.md

@@ -4260,7 +4260,7 @@ recommended.
 When `file` is a file descriptor, the behavior is almost identical to directly
 calling `fs.write()` like:
 
-```javascript
+```js
 fs.write(fd, Buffer.from(data, options.encoding), callback);
 ```
 

doc/api/stream.md

@@ -896,7 +896,7 @@ The `'readable'` event is emitted when there is data available to be read from
 the stream. In some cases, attaching a listener for the `'readable'` event will
 cause some amount of data to be read into an internal buffer.
 
-```javascript
+```js
 const readable = getReadableStreamSomehow();
 readable.on('readable', function() {
   // There is some data to read now.

doc/guides/writing-tests.md

@@ -29,7 +29,7 @@ For example, look for `test-streams` when writing a test for `lib/streams.js`.
 
 Let's analyze this basic test from the Node.js test suite:
 
-```javascript
+```js
 'use strict';                                                          // 1
 const common = require('../common');                                   // 2
 const fixtures = require('../common/fixtures');                        // 3
@@ -57,7 +57,7 @@ server.listen(0, () => {                                               // 14
 
 ### **Lines 1-3**
 
-```javascript
+```js
 'use strict';
 const common = require('../common');
 const fixtures = require('../common/fixtures');
@@ -78,13 +78,13 @@ the test leaks variables into the global space. In situations where a test uses
 no functions or other properties exported by `common`, include it without
 assigning it to an identifier:
 
-```javascript
+```js
 require('../common');
 ```
 
 ### **Lines 5-6**
 
-```javascript
+```js
 // This test ensures that the http-parser can handle UTF-8 characters
 // in the http header.
 ```
@@ -94,7 +94,7 @@ designed to test.
 
 ### **Lines 8-9**
 
-```javascript
+```js
 const assert = require('assert');
 const http = require('http');
 ```
@@ -136,7 +136,7 @@ In the event a test needs a timer, consider using the
 `common.platformTimeout()` method. It allows setting specific timeouts
 depending on the platform:
 
-```javascript
+```js
 const timer = setTimeout(fail, common.platformTimeout(4000));
 ```
 
@@ -155,7 +155,7 @@ One interesting case is `common.mustCall`. The use of `common.mustCall` may
 avoid the use of extra variables and the corresponding assertions. Let's
 explain this with a real test from the test suite.
 
-```javascript
+```js
 'use strict';
 require('../common');
 const assert = require('assert');
@@ -189,7 +189,7 @@ const server = http.createServer((req, res) => {
 
 This test could be greatly simplified by using `common.mustCall` like this:
 
-```javascript
+```js
 'use strict';
 const common = require('../common');
 const http = require('http');
@@ -216,7 +216,7 @@ provides a simple countdown mechanism for tests that require a particular
 action to be taken after a given number of completed tasks (for instance,
 shutting down an HTTP server after a specific number of requests).
 
-```javascript
+```js
 const Countdown = require('../common/countdown');
 
 const countdown = new Countdown(2, () => {
@@ -237,7 +237,7 @@ hence, the test fail - in the case of an `unhandledRejection` event. It is
 possible to disable it with `common.disableCrashOnUnhandledRejection()` if
 needed.
 
-```javascript
+```js
 const common = require('../common');
 const assert = require('assert');
 const fs = require('fs').promises;
@@ -257,7 +257,7 @@ test followed by the flags. For example, to allow a test to require some of the
 `internal/*` modules, add the `--expose-internals` flag.
 A test that would require `internal/freelist` could start like this:
 
-```javascript
+```js
 'use strict';
 
 // Flags: --expose-internals