Route

Web servers use the request's path and HTTP method to look up the correct resource, refers as "routing".

We can define a route by calling a method named after HTTP verbs, passing a path and a function to execute when matched.

import { Elysia } from 'elysia'

new Elysia()
    .get('/', () => 'hello')
    .get('/hi', () => 'hi')
    .listen(3000)

We can access the web server by going to http://localhost:3000

By default, web browsers will send a GET method when visiting a page.

localhost//hi

GET

TIP

Using an interactive browser above, hover on a blue highlight area to see difference result between each path

HTTP Verb

There are many HTTP methods to use in a different situation, for instance.

GET

Requests using GET should only retrieve data.

POST

Submits a payload to the specified resource, often causing state change or side effect.

PUT

Replaces all current representations of the target resource using the request's payload.

DELETE

Deletes the specified resource.

---

To handle each of the different verbs, Elysia has a built-in API for several HTTP verbs by default, similar to Elysia.get

import { Elysia } from 'elysia'

new Elysia()
    .get('/', () => 'hello')
    .post('/hi', () => 'hi')
    .listen(3000)

localhost//hi

GET

Elysia HTTP methods accepts the following parameters:

• path: Pathname
• function: Function to respond to the client
• hook: Additional metadata

You can read more about the HTTP methods on HTTP Request Methods.

Method Chaining

Rule of thumb, ALWAYS use method chaining in Elysia.

import { Elysia } from 'elysia'

// ❌ don't
const app1 = new Elysia()

app1.get('/', () => 'hello')

app1.post('/', () => 'world')

// ✅ do
const app = new Elysia()
    .get('/', () => 'hello')
    .post('/', () => 'world')

Elysia is using method chaining to synchronize type safety for later use.

Without method chaining, Elysia can't ensure your type integrity which will have of usage in later chapters.

Handle

Most developers use REST clients like Postman, Insomnia or Hoppscotch to test their API.

However, Elysia can be programmatically test using Elysia.handle.

import { Elysia } from 'elysia'

const app = new Elysia()
    .get('/', () => 'hello')
    .post('/hi', () => 'hi')
    .listen(3000)

app.handle(new Request('http://localhost/')).then(console.log)

Elysia.handle is a function to process an actual request sent to the server.

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Unlike unit test's mock, you can expect it to behave like an actual request sent to the server.

But also useful for simulating or creating unit tests.

Custom Method

We can accept custom HTTP Methods with Elysia.route.

import { Elysia } from 'elysia'

const app = new Elysia()
    .get('/get', () => 'hello')
    .post('/post', () => 'hi')
    .route('M-SEARCH', '/m-search', () => 'connect') 
    .listen(3000)

localhost/get/post/m-search

GET

Elysia.route accepts the following:

• method: HTTP Verb
• path: Pathname
• function: Function to response to the client
• hook: Additional metadata

When navigating to each method, you should see the results as the following:

Path	Method	Result
/	GET	hello
/	POST	hi
/	M-SEARCH	connect

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Based on RFC 7231, HTTP Verb is case-sensitive.

It's recommended to use the UPPERCASE convention for defining a custom HTTP Verb with Elysia.

Elysia.all

Elysia provides an Elysia.all for handling any HTTP method for a specified path using the same API like Elysia.get and Elysia.post

import { Elysia } from 'elysia'

new Elysia()
    .all('/', () => 'hi')
    .listen(3000)

localhost//

GET

Any HTTP method that matches the path, will be handled as follows:

Path	Method	Result
/	GET	hi
/	POST	hi
/	DELETE	hi

404

If no path matches the defined routes, Elysia will pass the request to error life cycle before returning a "NOT_FOUND" with an HTTP status of 404.

We can handle a custom 404 error by returning a value from 'error` life cycle like this:

import { Elysia } from 'elysia'

new Elysia()
    .get('/', () => 'hi')
    .onError(({ code }) => {
        if (code === 'NOT_FOUND')
            return 'Route not found :('
    })
    .listen(3000)

localhost//hi

GET

When navigating to your web server, you should see the result as follows:

Path	Method	Result
/	GET	hi
/	POST	Route not found :(
/hi	GET	Route not found :(

You can learn more about life cycle and error handling in Life Cycle Events and Error Handling.

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HTTP Status is used to indicate the type of response. By default if everything is correct, the server will return a '200 OK' status code (If a route matches and there is no error, Elysia will return 200 as default)

If the server fails to find any route to handle, like in this case, then the server shall return a '404 NOT FOUND' status code.