merge dev into main

Author: DucMinhNe

.editorconfig

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+root = true
+
+[*]
+indent_style = space
+indent_size = 2
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true

.github/workflows/ci.yml

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+name: CI
+on:
+  push:
+    branches: [main]
+  pull_request:
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
+      - run: npm ci
+      - run: npm test

topics/async-promises/README.md

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+# Promises & async/await
+
+Promises represent a future value. async/await is sugar over .then chains.
+
+## Key points
+
+- 3 states: pending, fulfilled, rejected
+- Promise.all / race / allSettled / any
+- always handle rejections
+- common pitfall: forgetting `await`
+
+## Examples
+
+See `examples/` for runnable demos.
+
+## Exercise
+
+Convert a callback-based API client to async/await.
+
+See `exercise.js` for the starter.

topics/async-promises/examples/01-basic.js

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+// promise chaining
+function fetchUser(id) {
+  return new Promise((resolve) => {
+    setTimeout(() => resolve({ id, name: 'user_' + id }), 20);
+  });
+}
+
+fetchUser(1)
+  .then((u) => { console.log(u); return fetchUser(u.id + 1); })
+  .then((u) => console.log(u))
+  .catch(console.error);

topics/async-promises/examples/02-async-await.js

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+// async/await
+async function loadAll(ids) {
+  const results = [];
+  for (const id of ids) {
+    const u = await fetchUser(id);
+    results.push(u);
+  }
+  return results;
+}
+
+// parallel
+async function loadAllParallel(ids) {
+  return Promise.all(ids.map(fetchUser));
+}

topics/async-promises/examples/03-pitfalls.js

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+// common pitfall: forgetting to await
+async function bad() {
+  const result = fetchUser(1); // missing await -> returns a Promise, not the user
+  console.log(result.name);    // undefined
+}
+
+async function good() {
+  const result = await fetchUser(1);
+  console.log(result.name);
+}

topics/async-promises/exercise.js

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+// Exercise: Convert a callback-based API client to async/await.
+// TODO: implement
+module.exports = {};

topics/best-practices/README.md

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+# Production checklist
+
+What I want students to remember after the course.
+
+## Key points
+
+- validate input at the boundary
+- 12-factor config (env vars, logs to stdout)
+- graceful shutdown
+- structured logging, not `console.log`
+- don't block the event loop
+
+## Examples
+
+See `examples/` for runnable demos.
+
+## Exercise
+
+Audit a sample Express app against the checklist.
+
+See `exercise.js` for the starter.

topics/best-practices/examples/01-checklist.js

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+// don't:
+// - log secrets, tokens, full request bodies
+// - use synchronous fs in hot paths
+// - swallow errors silently
+// - pass user input to child_process.exec directly
+// - block the event loop with CPU work — use worker_threads
+
+// do:
+// - validate input at the boundary (zod, joi)
+// - 12-factor: config in env, logs to stdout
+// - graceful shutdown on SIGTERM
+// - prefer async fs APIs
+// - use a process manager (pm2, systemd, k8s)

topics/best-practices/exercise.js

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+// Exercise: Audit a sample Express app against the checklist.
+// TODO: implement
+module.exports = {};