Update a query parameter Node.js

Question

using Node.js / Express I am defining a path, passing in a request and response.

I always want to include a seed url parameter when this path is hit so I set that seed query param to 0 and redirect the url.

What I want to do next is randomize that parameter with each request/response and update the url based on the additional of another url param, in this case random=true .

Default route should look like localhost:3000/default?seed=0

Route if the random=true parameter is used could look like localhost:3000/default?seed=456&random=true where the seed is updated on each request.

My code (server.js using express, canvas, and url modules):

`app.get("/default", (req, res) => { 

 //some logic to generate random numbers for the seed parameter
 let seed = Math.round(Math.ceil(Math.random() * parseInt(req.query.seed + 1) * 100))

 // if we hit the path and no seed param is defined always give it zero
 if(!req.query.seed) { 
    req.query.seed = 0; 

    res.redirect(url.format({ // redirect the url with the new param 
      pathname: '/canvas',
      query: req.query
    }))
 }

 //if we hit the path and the random param is set to true and there is a seed parameter
 if(req.query.random === 'true' && req.query.seed) {
   req.query.seed = seed; // use randomized seed as the new seed param value

   res.redirect(url.format({ // redirect to the url with the updated seed
      pathname: '/canvas',
      query: req.query
   }))

   //render our response
   canvas(req, res);
});`

What I see: The url does appear to be updating I get results such as:

/default?seed=115&random=true, /default?seed=21457&random=true, etc

However my canvas does not render and I get a too many redirects error in the browser localhost redirected you too many times.

I don't have a great knowledge of redirect concepts in Node but would appreciate it if someone could point me in the right direction so that this is no longer an error. Thanks

Answer 1

Your issue is you are infinitely redirecting. When the user arrives at /default you create your query params... and redirect them back to /default with the query params, where you then again update the query params, and send them to /default forever. Your browser realizes you're trapped in an infinite loop and breaks you out of it with the "too many redirects" error. You need a break condition around your redirect.

Maybe

if(!res.query){
   res.redirect(url.format({ // redirect to the url with the updated seed
      pathname: '/canvas',
      query: req.query
   }))
}