README
express-lazy-router
Lazy loading for express router.
Motivation
I've used ts-node(ts-node-dev) for developing Node.js Web Application. It means that compile all TypeScript files at start time.
Many compilation make startup of the web app slow. Lazy routing avoid this compilation overhead by compiled when needed.
In a frontend, We have already used lazy loading for router like React Router, Vue Router.
Also, webpack support experiments.lazyCompilation as experimentally.
So, We can get lazy routing in Node.js Express routing too.
Install
Install with npm:
npm install express-lazy-router
Usage
import express from 'express';
import { createLazyRouter } from 'express-lazy-router';
const lazyLoad = createLazyRouter({
// In production, Load router asap
preload: process.env.NODE_ENV === 'production',
});
const app = express();
// Load ./path_to_router.js when receive request to "/path_to_router"
app.use(
'/path_to_router',
lazyLoad(() => import('./path_to_router')),
);
app.listen(8000, () => {
console.log(`Example app listening at http://localhost:8000`)
});
Options
preload
Default: false
If it is true
, preload the router module as soon as.
It does not mean sync loading.
Examples
Before: No lazy loading
index.js
:
import express from 'express';
import api from "./api";
const app = express();
app.use(
'/api',
api
);
app.listen(8000, () => {
console.log(`Example app listening at http://localhost:8000`)
});
api.js
:
import express from 'express';
const router = express.Router();
// GET api/status
router.get("/status", (_, res) => {
res.json({ ok: true })
});
export default router;
Behavior:
- load
index.js
- load
api.js
- complete to launch the express app
GET /api/status
{ ok: true }
After: lazy loading for api.js
index.js
:
import express from 'express';
- import api from "./api";
+ import { createLazyRouter } from 'express-lazy-router';
+ const lazyLoad = createLazyRouter({
+ preload: process.env.NODE_ENV === 'production',
+ });
const app = express();
app.use(
'/api',
- api
+ lazyLoad(() => import("./api"))
);
app.listen(8000, () => {
console.log(`Example app listening at http://localhost:8000`)
});
api.js
: No need to change!
Behavior:
- load
index.js
- complete to launch the express app
GET /api/status
- load
api.js
{ ok: true }
The more details behavior when you use loader like @babel/register or ts-node.
- load
index.js
- Compile
index.js
by babe;
- Compile
- complete to launch the express app
GET /api/status
- load
api.js
- Compile
api.js
by babe;
- Compile
{ ok: true }
Limitation
Avoid to use non-path router
NG: express-lazy-router does not expect this way.
import { createLazyRouter } from 'express-lazy-router';
const lazyLoad = createLazyRouter();
const app = express();
app.use(
lazyLoad(() => import('./path_to_router')),
);
app.listen(port, () => {
console.log(`Example app listening at http://localhost:${port}`)
});
Changelog
See Releases page.
Running tests
Install devDependencies and Run npm test
:
npm test
Contributing
Pull requests and stars are always welcome.
For bugs and feature requests, please create an issue.
- Fork it!
- Create your feature branch:
git checkout -b my-new-feature
- Commit your changes:
git commit -am 'Add some feature'
- Push to the branch:
git push origin my-new-feature
- Submit a pull request :D
Author
License
MIT © azu