koa
Provides comprehensive guidance for Koa.js framework including middleware composition, context API, async/await patterns, and application structure. Use when the user asks about Koa, needs to create lightweight Node.js web applications, implement middleware, or build APIs with Koa.
Best use case
koa is best used when you need a repeatable AI agent workflow instead of a one-off prompt. It is especially useful for teams working in multi. Provides comprehensive guidance for Koa.js framework including middleware composition, context API, async/await patterns, and application structure. Use when the user asks about Koa, needs to create lightweight Node.js web applications, implement middleware, or build APIs with Koa.
Provides comprehensive guidance for Koa.js framework including middleware composition, context API, async/await patterns, and application structure. Use when the user asks about Koa, needs to create lightweight Node.js web applications, implement middleware, or build APIs with Koa.
Users should expect a more consistent workflow output, faster repeated execution, and less time spent rewriting prompts from scratch.
Practical example
Example input
Use the "koa" skill to help with this workflow task. Context: Provides comprehensive guidance for Koa.js framework including middleware composition, context API, async/await patterns, and application structure. Use when the user asks about Koa, needs to create lightweight Node.js web applications, implement middleware, or build APIs with Koa.
Example output
A structured workflow result with clearer steps, more consistent formatting, and an output that is easier to reuse in the next run.
When to use this skill
- Use this skill when you want a reusable workflow rather than writing the same prompt again and again.
When not to use this skill
- Do not use this when you only need a one-off answer and do not need a reusable workflow.
- Do not use it if you cannot install or maintain the related files, repository context, or supporting tools.
Installation
Claude Code / Cursor / Codex
Manual Installation
- Download SKILL.md from GitHub
- Place it in
.claude/skills/koa/SKILL.mdinside your project - Restart your AI agent — it will auto-discover the skill
How koa Compares
| Feature / Agent | koa | Standard Approach |
|---|---|---|
| Platform Support | Not specified | Limited / Varies |
| Context Awareness | High | Baseline |
| Installation Complexity | Unknown | N/A |
Frequently Asked Questions
What does this skill do?
Provides comprehensive guidance for Koa.js framework including middleware composition, context API, async/await patterns, and application structure. Use when the user asks about Koa, needs to create lightweight Node.js web applications, implement middleware, or build APIs with Koa.
Where can I find the source code?
You can find the source code on GitHub using the link provided at the top of the page.
SKILL.md Source
## When to use this skill
Use this skill whenever the user wants to:
- Build Node.js HTTP services with Koa and its onion-model middleware
- Configure routing (koa-router), body parsing, error handling, and static files
- Compose async middleware with `ctx` and `next` patterns
- Create lightweight REST APIs or web applications
## How to use this skill
### Workflow
1. **Create app** — instantiate Koa and add middleware in order
2. **Add routing** — use `@koa/router` for route definitions
3. **Handle errors** — add error middleware at the top of the stack
4. **Deploy** — run behind reverse proxy with HTTPS
### Quick Start Example
```javascript
const Koa = require('koa');
const Router = require('@koa/router');
const bodyParser = require('koa-bodyparser');
const app = new Koa();
const router = new Router();
// Error handling middleware (top of stack)
app.use(async (ctx, next) => {
try {
await next();
} catch (err) {
ctx.status = err.status || 500;
ctx.body = { error: err.message };
ctx.app.emit('error', err, ctx);
}
});
// Body parser
app.use(bodyParser());
// Routes
router.get('/api/items', async (ctx) => {
const items = await Item.findAll();
ctx.body = { items };
});
router.post('/api/items', async (ctx) => {
const { name, price } = ctx.request.body;
const item = await Item.create({ name, price });
ctx.status = 201;
ctx.body = item;
});
router.get('/api/items/:id', async (ctx) => {
const item = await Item.findById(ctx.params.id);
if (!item) {
ctx.throw(404, 'Item not found');
}
ctx.body = item;
});
app.use(router.routes());
app.use(router.allowedMethods());
app.listen(3000, () => console.log('Server running on port 3000'));
```
### Onion Model Middleware
```javascript
// Logging middleware — demonstrates onion execution order
app.use(async (ctx, next) => {
const start = Date.now();
await next(); // <-- downstream
const ms = Date.now() - start;
ctx.set('X-Response-Time', `${ms}ms`);
console.log(`${ctx.method} ${ctx.url} - ${ms}ms`);
});
```
### Custom Middleware Example
```javascript
// Authentication middleware
function requireAuth() {
return async (ctx, next) => {
const token = ctx.get('Authorization')?.replace('Bearer ', '');
if (!token) {
ctx.throw(401, 'Authentication required');
}
ctx.state.user = await verifyToken(token);
await next();
};
}
router.get('/api/profile', requireAuth(), async (ctx) => {
ctx.body = ctx.state.user;
});
```
## Best Practices
- Use `async/await` correctly with `next()` — always `await next()` in middleware
- Place error handling middleware at the top of the middleware stack
- Use `ctx.throw()` for HTTP errors; listen to `app.on('error')` for logging
- Deploy behind a reverse proxy (nginx) with HTTPS in production
- Use `@koa/cors` for CORS configuration; keep middleware chain lean
## Reference
- Official documentation: https://koajs.com/
## Keywords
koa, Node.js, middleware, onion model, async/await, context, routing, REST APIRelated Skills
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