Event Object
Event object carries an incoming request and context.
Everytime a new HTTP requerst comes, h3 internally create an Event object and passes it though event handlers until sending response.
An event is passed through all the lifecycle hooks and composable utils to use it as context.
Example:
import { defineEventHandler, getQuery, readBody } from "h3";
app.use(defineEventHandler((event) => {
// Log event. `.toString()` stringifies to a simple string like `[GET] /<path>`
console.log(`Request: ${event.toString()}`);
// Parse query parms
const query = getQuery(event)
// Try to read request body
const body = await readBody(event).catch(() => {})
// Echo back request as response
return {
path: event.path,
method: event.method,
query,
body,
}
}));
Properties
The main properties of an event are:
event.node
The event.node allows to access the native Node.js request and response. In runtimes other than Node.js/Bun, h3 makes a compatible shim using unjs/unenv.
event.node.* context as much as you can and instead prefer h3 utils.defineEventHandler((event) => {
event.node.req; // Node.js HTTP Request
event.node.res; // Node.js HTTP Response
});
event.web?
Only if available, it is an object with request and url propertiers to access native web request context.
event.method
Access to the normalized (uppercase) request method.
event.path
Access to the request request path. (Example: /test?test=123)
contextwith some context information about the request.headerswith a normalized version of the headers of the request.handledwith a boolean that indicates if the request has terminated.
event.headers
Access tp the normalized request Headers.
getHeaders(event) or getHeader(event, name) for a simplified interface.event.context
The context is an object that contains arbitrary information abut the request.
You can store your custom properies inside event.context to share across composable utils.
event.handled
Specifies if response is already handled or not. Initially for each request it is false and when a response is generated, it is set to true.
Advanced: If you manually handle the response, set it to true to tell h3 stop sending any responses.
Methods
Actually, h3 provide a function to help you to create a response before the end of the request.
event.respondWith
The respondWith method is used to create a response without ending the request.
You must craft a response using the Response constructor.
return over respondWith as best practice.responseWith will always take precedence over the returned value, from current and next event handlers. If there is no returned value, the request will continue until the end of the stack runner.Example:
defineEventHandler((event) => {
await event.respondWith(new Response("Hello World"));
return "..."; // DOES NOT WORKS
});
app.use(
defineEventHandler((event) => {
await event.respondWith(new Response("Hello World"));
return "..."; // DOES NOT WORK
}),
);
With this example, the client will receive Hello World.