Return JSON

js

export default {
  async fetch(request) {
    const data = {
      hello: "world",
    };

    return Response.json(data);
  },
};

Run Worker in Playground

ts

export default {
  async fetch(request): Promise<Response> {
    const data = {
      hello: "world",
    };

    return Response.json(data);
  },
} satisfies ExportedHandler;

py

from js import Response, Headers
import json

def on_fetch(request):
    data = json.dumps({"hello": "world"})
    headers = Headers.new({"content-type": "application/json"}.items())
    return Response.new(data, headers=headers)

rs

use serde::{Deserialize, Serialize};
use worker::*;

#[derive(Deserialize, Serialize, Debug)]
struct Json {
    hello: String,
}

#[event(fetch)]
async fn fetch(_req: Request, _env: Env, _ctx: Context) -> Result<Response> {
    let data = Json {
        hello: String::from("world"),
    };
    Response::from_json(&data)
}