Journal

Progress

• Node.js 24.21.0 installed on Windows, and in CI on Linux, Windows and macOS with .NET 10 and Java 25
• CI: examples, error snippets, solutions and the C# and Java comparisons compared with their expected output on three OSes
• Lesson 1: Node.js, npm and modules
• Lesson 2: values and types
• Lesson 3: functions, scope, closures and this
• Lesson 4: objects, prototypes and classes
• Lesson 5: arrays, iteration and collections

2026-09-14 — Installing Node.js 24.21.0

• The release index lists 24.21.0, published on 2026-09-07, as the latest LTS release, and 26.8.2 as the latest current release. Node.js 26 becomes LTS on 2026-10-28, according to the schedule.
• My machine already had a global Node.js 24.12.0. I left it alone, downloaded node-v24.21.0-win-x64.zip into a folder of its own, checked its SHA-256 against SHASUMS256.txt, and put that folder first on the PATH of the shells that capture the lessons’ outputs. node -p process.versions.v8 prints 13.6.233.17-node.53; the bundled npm is 11.19.0.
• The PowerShell commands of lesson 1 downloaded, checked and expanded the archive in 22 seconds, in a scratch folder.
• winget show OpenJS.NodeJS.LTS offered 24.19.0, two releases behind nodejs.org.

2026-09-14 — The CI

• javascript-examples.yml installs Node.js 24.21.0 with actions/setup-node@v7, .NET 10 and Java 25, and runs check.sh. The first push passed on the three OSes in 1 minute 28 seconds: the 52 outputs captured on Windows are identical on Linux and macOS.
• Node.js prints absolute paths in its errors, as a file URL, a Windows path, or even a Windows path with the \\?\ long-path prefix, as in the message about package.json in lesson 1. normalize.mjs makes them relative to the course folder, removes the stack frames and replaces process IDs.
• The C# comparison first printed 1.0 / 0 as ∞, the infinity symbol of my culture’s number format; it now sets CultureInfo.InvariantCulture, which prints Infinity on every machine. Java printed the guitar emoji as ? in the Windows console, so the comparison programs print only ASCII.
• The CI also installs @esbuild/win32-x64@0.25.12 as a development dependency on each OS, for lesson 1: npm installs it on Windows and stops with EBADPLATFORM on Linux and macOS.

2026-09-14 — Surprises while writing lessons 1-4

Node.js’s “Did you mean to import” hint depends on the current folder. An ES module import without its extension fails with ERR_MODULE_NOT_FOUND, and Node.js adds a hint with the right path, but only when the command runs from a folder where that relative path also exists. resolveAsCommonJS creates a CommonJS parent module whose file name is never set (resolve.js, lines 888-895), and for a parent without a file name the CommonJS resolver looks from '.' (loader.js, lines 1021-1028). The code is the same on Node.js’s main branch. I found no issue about it with a search for “Did you mean to import” in nodejs/node. check.sh runs the error snippets from their own folder, and runs this one a second time from the course folder, without the hint.

A duplicate function is an error at the top of a module only. Two function describe declarations in the same ES module are a SyntaxError before anything runs; the same two declarations inside a function body, or at the top of a CommonJS file, are accepted, and the second one wins. I had written the duplicate at the top level of the lesson 3 example to show the silent replacement, and got the error instead.

[1, 2, 3].map(multiply) prints [ 0, 2, 6 ]. I passed multiply to map as a harmless example that functions are values, and map passed the index as the second argument. The example stayed in lesson 3, as the trap it is, next to ['1', '2', '3'].map(parseInt).

npm init -y writes "type": "commonjs". npm 11.19 adds the field explicitly; older templates left it out, which made .js files CommonJS by default all the same.

A .cjs file with import gets advice that doesn’t apply. Node.js prints Warning: Failed to load the ES module … Make sure to set "type": "module" in the nearest package.json file or use the .mjs extension, then the SyntaxError. The "type" field can’t help a .cjs file: its extension wins.

require of an ES module works without a warning. Node.js 24.21.0 loads modern.mjs from from-cjs.cjs silently; the documentation says the feature stopped being experimental in 24.15.0. With a top-level await in the module, require throws ERR_REQUIRE_ASYNC_MODULE, which I checked for the solution of exercise 1.

pnpm doesn’t check the platform of a direct dependency. In a scratch project on Windows, npx pnpm@10 add -D @esbuild/linux-x64@0.25.12 installed the Linux package without a warning (pnpm 10.34.5), where npm refuses it with EBADPLATFORM.

2026-09-14 — What GuitarAlchemist/ga’s front end showed (a826864)

I read ReactComponents/ga-react-components and Apps/ga-client at commit a826864, looking for the traps of lessons 1 to 4.

• Two lock files. Apps/ga-client has a package-lock.json and a pnpm-lock.yaml; nothing keeps the two resolutions in agreement.
• A Windows-only package in devDependencies. ga-react-components/package.json, line 71 lists @esbuild/win32-x64. The course’s CI shows that npm refuses that exact package on Linux and macOS; the folder only has a pnpm-lock.yaml, and pnpm installed a foreign platform package without complaint on my machine, so the project probably installs with pnpm everywhere (to verify on Linux).
• A saved state that beats the URL. In SceneOptions.tsx, the URL parameters are applied before Object.assign merges the preferences saved in localStorage, and every toggle saves every key. After the first toggle, ?tower, ?constellations, ?weather, ?skybox and ?splats no longer change anything. The merge also keeps unknown keys and values of the wrong type, and a __proto__ key replaces the state object’s prototype. Lesson 4 reproduces the three, and its exercise 3 fixes them. This looks like a bug worth an issue.
• || 0.5 where ?? is meant. BSPDoomExplorer.tsx, line 4895 would turn a rotation speed of 0 into 0.5. No sample gets a speed of 0 today, so it is latent. Line 5386 works because NaN is falsy, not because of the grouping it seems to have.
• Event listeners are right. The seven addEventListener calls of the two front ends that pass a this.… handler use either a function bound once and stored, or an arrow function stored in a field, and none binds inline; lesson 3 runs the three patterns.
• Loose equality only for null. The TypeScript sources use == and != only as == null and != null; the other matches are GLSL shader code in strings. Their ESLint configurations extend js.configs.recommended, which doesn’t enable eqeqeq.
• parseInt without a radix, in BSPDoomExplorer.tsx, line 2421 and MusicRoomLoader.ts, lines 209-211. The inputs are decimal digits from a name or a regular expression match, so it is harmless there.

To verify

• The installation commands I haven’t run: winget install OpenJS.NodeJS.LTS, nvm on Linux, and Homebrew’s node@24 on macOS.
• Whether pnpm install of ga-react-components succeeds on Linux and macOS with @esbuild/win32-x64 in its development dependencies.