express routes share variable - express

Question

I can't share var between routes in my index.js. I need to use var page from first route in the second route. Is necesary a closure for this? I have this two routes:
First route:
router.get('/:page', async (req, res, next) =>{
var perPage = 5;
var page = req.params.page || 1;
console.log(page);
const expedientes = await Expediente
.find()
.skip((perPage*page)-perPage)
.limit(perPage)
.exec((err, expedientes)=> {
Expediente.count().exec((err, count)=> {
if (err) return next(err)
res.render('index', {
expedientes,
current: page,
pages: Math.ceil(count / perPage)
})
})
})
});
Second route:
router.get('/select/:id', async (req,res) => {
const { id } = req.params;
const {path} = req.path;
const expediente = await Expediente.findOne({selected:true});
const expediente2 = await Expediente.findById(id);
if (expediente){
expediente.selected=!expediente.selected;
await expediente.save();
}
expediente2.selected=!expediente2.selected;
await expediente2.save();
res.redirect('/1');
});
I need to use var page for the last line of the second route. How can i get that value to use it? I have try:
res.redirect('/'+ page);
but it doesn't work.
Some information about this problem?

Answer 1

You should probably avoid keeping the front-end state in your backend. In order to avoid this you can introduce a query parameter with the redirect
router.get('/select/:id', async ( req, res ) => {
const { id } = req.params;
const {path} = req.path;
const expediente = await Expediente.findOne({selected:true});
const expediente2 = await Expediente.findById(id);
const page = req.query.page;
if (expediente){
expediente.selected=!expediente.selected;
await expediente.save();
}
expediente2.selected=!expediente2.selected;
await expediente2.save();
res.redirect('/' + page);
});
Then you should call the URL with /select/2?page=1 which will redirect you to the page.
In your solution when you have two routes called by two different clients will have the very same page being defined, which is not what you probably want.

Answer 2

The solution is not easy. In my app I have two different needs. Both, need to obtain data from the database.
The first is pagination, each time a pagination-button is pressed, the database must be consulted to obtain the set of records for that page-pagination.
The second is the record-selection, it also need the database because when you select a record the id is stored so that the delete and edit buttons can act. All this works perfectly.
But the problem is when I select a record and also I advance in the pagination and select again other record. when the page is loaded again, I can not find a way to redirect back to the page from which it came. That is the page-pagination where the second record was selected.
So I thought that saving the last page in a variable, I could use that variable to redirect back in other route.
My question therefore is: can I save res.params.page in a variable and then use that varible in a different route?