Handler#

To route is to tell which function should return a response.

The function for returning a Response is Handler.

Handler is a callback function which accept Context, helping you access powerful API for accessing data and modifying the response.

The params from the previous example also come from Handler

// Structure
app.get(path, handler, hook?)

// Usage
app.get('/id/:id', (context) => context.params.id)

Context#

Context's properties consists of

• request: Raw Request for accessing data as web standard type
• body: Body which come with the request
• query: Parsed path query as a simple object
• params: Path parameters as a simple object
• store: A global mutable store for Elysia instance
• set: Response representation
  • status: response status
  • headers: response headers
  • redirect: redirect to new path

You can access Context in Handler function:

app.post("/", ({ body, set }) => {
  const signed = signIn(body);

  if (signed) return "Welcome back";

  set.status = 403;
  return "Invalid username or password";
});

Response#

Returning value from Handler, Elysia will try to map returned value into Response.

For example, to return an object, you should stringify the content first and then set response header of Content-Type to application/json.

Which look something like this:

new Response(
  JSON.stringify({
    vtuber: ["Shirakami Fubuki", "Inugami Korone"],
  }),
  {
    headers: {
      "Content-Type": "application/json",
    },
  }
);

But Elysia handles that for you.

You simply return an object, and Elysia will map your value to a correct response for you.

app.get("/", () => ({
  vtuber: ["Shirakami Fubuki", "Inugami Korone"],
}));

Of course, as Elysia map the value to Response.

But you can also return a Response if you really want to.

app.get(
  "/",
  () =>
    new Response(
      JSON.stringify({
        vtuber: ["Shirakami Fubuki", "Inugami Korone"],
      }),
      {
        headers: {
          "Content-Type": "application/json",
        },
      }
    )
);