Show XX items per page problem

[drummerooo]

Hello,

based on topic 

i implemented solution for choosing items per page by user.

More less it's working quite good but have problem in two cases at least:

1. When user firstly choose some filter for products and then will need to choose results per page then filter is clear.

2. When user uses "search" and with search result will choose items per page then no items are show.

Example webpage is: https://e-m2.pl/

 

I found what is causing this problem:

 

Everytime when user will check some checkbox with filter and then press "results per page" option from dropdown then in URL is only "https://xxxxx.com/xxxx?resultsPerPage=48 but if some filter is checked and basic URL is https://xxxxx.com/xxxxx?filter and then user will choose some "result per page" option then in URL it should be https://xxxxx.com/xxxxx?filter&resultsPerPage=48 but now filter is replaced by only ?resultsPerPage=xx.

If filter is checked or "?" is already added in URL then it should only add &

 

How to fix it ?

 

Thank you in advance.