js Posts - Deno

•Created by js on 5/15/2025 in #help

ReadableStream doesn't work in production

I'm following the Deno SSE example to set up a GET route for SSE payloads. Exact I got from the SSE examples works ONLY in local development. In production, the requests are stuck in "pending" forever. Is there something different about localhost and production environment that I have to change?

app.get('/test-sse', (c: Context) => {
        let timerId: number | undefined;
        const body = new ReadableStream({
            start(controller) {
                const encoder = new TextEncoder();
                timerId = setInterval(() => {
                    const streamMessage = JSON.stringify({
                        message: `Hello world ${new Date().toISOString()}`,
                    });

                    controller.enqueue(new TextEncoder().encode(`data: ${streamMessage}\r\n\r\n`));
                }, 1000);
            },
            cancel() {
                if (typeof timerId === 'number') {
                    clearInterval(timerId);
                }
            },
        });



        return new Response(body, {
            headers: {
                'Content-Type': 'text/event-stream',
                'Cache-Control': 'no-cache',
                'Connection': 'keep-alive',
            },
        });
    });

app.get('/test-sse', (c: Context) => {
        let timerId: number | undefined;
        const body = new ReadableStream({
            start(controller) {
                const encoder = new TextEncoder();
                timerId = setInterval(() => {
                    const streamMessage = JSON.stringify({
                        message: `Hello world ${new Date().toISOString()}`,
                    });

                    controller.enqueue(new TextEncoder().encode(`data: ${streamMessage}\r\n\r\n`));
                }, 1000);
            },
            cancel() {
                if (typeof timerId === 'number') {
                    clearInterval(timerId);
                }
            },
        });



        return new Response(body, {
            headers: {
                'Content-Type': 'text/event-stream',
                'Cache-Control': 'no-cache',
                'Connection': 'keep-alive',
            },
        });
    });

4 replies

DDeno

•Created by js on 5/30/2024 in #help

VS Code Settings

3 replies

DDeno

•Created by js on 5/28/2024 in #help

A way to render code only if JS code can't be run

I noticed (at least in development), that when the app refreshes due to code change, and if I press back button to go to a previous version of the app which is no longer valid, the app doesn't work (rightfully so, because the previous iteration of the dev app no longer exists). Interestingly, I noticed that the HTML code generated by previous version of the now non-existent app, stilll works. But this previous version of the app is static HTML, and JS does not work until I refresh the app. I'd like to know if it's possible to show a different code to ask the user to "refresh the page" if a user reaches this problem. Note: I have not tested this in production, so I do not know if this is a problem in production.

2 replies

DDeno

•Created by js on 5/26/2024 in #help

Route redirect handlers

I tried using this code to redirect a route to another route.

export const handler: Handlers = {
  GET(_req: Request, _ctx: FreshContext) {
    const headers = new Headers();
    headers.set('location', '/c/xyz');
    return new Response(null, {
      status: 302,
      headers,
    });
  },
};

export const handler: Handlers = {
  GET(_req: Request, _ctx: FreshContext) {
    const headers = new Headers();
    headers.set('location', '/c/xyz');
    return new Response(null, {
      status: 302,
      headers,
    });
  },
};

It works-- its loading "/c/xyz" (correctly, as it should). But the URL doesnt' change. Is there a way to make this work AND change the URL?

9 replies

DDeno

•Created by js on 5/25/2024 in #help

Using Deno.KV twice

I want to use Deno.kv twice. One in local memory and 1 persistent in database shared across multiple instances. Is that a good idea? And to do that, should I open two instances of Deno.openKv() in my app?

3 replies

DDeno

•Created by js on 5/22/2024 in #help

Which standard lib do I use?

I see the docs referencing https://deno.land/std/ But I thought JSR is the new shiny thing? And everythign is referencing jsr:@std. So which stnardard lib do I use?

3 replies

DDeno

•Created by js on 5/20/2024 in #help

Does preact useSignal() values need to be cleared for memory leak?

In react, I often had to do a if (mounted.current) {...} test to do something with reactive variables like states if I'm setting/using it after a Promise. If I use useSignal() from Preact, do I still have to check for if (mounted.current) {...} ?

1 replies

DDeno

•Created by js on 5/17/2024 in #help

Should I be using memo() in Fresh (/components/ folder)?

If Fresh renders the files in /components/ folder as html, and returns no javascript, should I ever bother using memo() in anything inside the components folder?

1 replies

DDeno

•Created by js on 5/16/2024 in #help

Deno Fresh: client side check dev or production

For my Deno Fresh app, I want to do a simple check from the client-side code to see whether it's in development mode or production deployed mode. Use case is: I want to point my API to my localhost if it's in development, otherwise point the API to production server. How can I do this in Deno Fresh?

2 replies

DDeno

•Created by js on 5/16/2024 in #help

Deno is not defined

Is "Deno" supposed to be defined on the front-end client? I'm trying to get a simple app working using Fresh framework, but even on a fresh install of Fresh app, Deno is not defined in client, which causes a LOT of necessary Deno modules to not work (for example, "graphql-request"). Is this a bug on Deno? Or is there another way I'm suppose to do this?

3 replies