Koa is being executed twice per request?

Question

Is there any reason why Koa is being executed twice per request?

const Koa = require('koa')
const app = new Koa()

const index = async(ctx, next) => {
  console.log('Hello world!')
  await next()
  ctx.body = 'Hello world!'
}

app.use(index);

app.listen(3000)

On my terminal, I get:

Hello world!
Hello world!

Any ideas?

Add a handler for `/favicon.ico`. Or this: https://stackoverflow.com/a/13416784 — robertklep, Sep 02 '17 at 13:10
I wanna help you but my node doesn't download koa module for some reason — Ahmed Can Unbay, Sep 02 '17 at 13:11
@robertklep it seems fixed with favicon.ico. but why does it do that without a favicon.ico? — Run, Sep 02 '17 at 13:19
Because your `index` handler matches _any_ request. And browsers typically try to retrieve `/favicon.ico` for a page, so you'll get two requests: one for the page, and one to see if there's a favicon for it. — robertklep, Sep 02 '17 at 13:19

Sebastian Hildebrandt · Accepted Answer · 2023-06-23T09:30:28.837

There are two reasons why this could happen:

First is - as already mentioned in the comments that browsers also fire a request for favicon.ico Second: some browsers do a prefentching, so before you even hit the return key, they prefetch the url when entering.

const Koa = require('koa')
const app = new Koa()

const index = async(ctx, next) => {
  console.log('URL --> ' + ctx.request.url); // This logs out the requested route
  console.log('Hello world!')
  await next()
  ctx.body = 'Hello world!'
}

app.use(index);

app.listen(3000)

I added one line to your code so that you can see which routes your browser asks for. This might help identify the reason for your problem.

Correct: most of the time it's just the browser asking for `/favicon.ico` as @robertklep has pointed out. even when specifying the type to be `application/json` the browser still does that. — jadinerky, Jun 22 '23 at 13:16

Koa is being executed twice per request?

1 Answers1