Handler and context

Handler - a resource or a route function to send data back to client.

import { Elysia } from 'elysia'

new Elysia()
    // `() => 'hello world'` is a handler
    .get('/', () => 'hello world')
    .listen(3000)

A handler can also be a literal value, see Handler

import { Elysia } from 'elysia'

new Elysia()
    // `'hello world'` is a handler
    .get('/', 'hello world')
    .listen(3000)

Using an inline value can be useful for static resources like files.

Context

Contains information about each request. It is passed as the only argument of a handler.

import { Elysia } from 'elysia'

new Elysia()
  .get('/', (context) => context.path)
            // ^ This is a context

Context stores information about the request like:

body - data sent by client to server like form data, JSON payload.
query - query string as an object. (Query is extracted from a value after pathname starting from ’?’ question mark sign)
params - Path parameters parsed as object
headers - HTTP Header, additional information about the request like “Content-Type”.

See Context.

Preview

You can preview the result by looking under the editor section.

There should be a tiny navigator on the top left of the preview window.

You can use it to switch between path and method to see the response.

You can also click to edit body, and headers.

Assignment

Let’s try extracting context parameters:

Assignments

0 of 4 assignments passed

Create POST endpoint
Not passed yet
Let's create a POST endpoint "/", so we can send a body
Extract body
Not passed yet
Let's extract a body and return it as `return { body }`
Extract query
Not passed yet
Let's extract a query and return it as `return { body, query }`
Extract headers
Not passed yet
Let's extract a header and return it as `return { body, query, headers }`

We can extract body, query, and headers from the first parameter of a callback function.
We can then return them like { body, query, headers }.

import { Elysia } from 'elysia'

new Elysia()
  .post('/', ({ body, query, headers }) => {
    return {
      query,
      body,
      headers
    }
  })
  .listen(3000)

One sec, warming things up…

Create POST endpoint

Extract body

Extract query

Extract headers