Node js or squid proxy to modify body of http (https) request (not headers)

Dear all, We have a javascript file that generates some API fetch in chrome browser. Now I want to modify some parameters in the body of one request. Please note that we can’t edit source of javascript file and modification must be done after generating fetch. I have tried many google chrome extensions and most of them only modify headers of http requests. Additionally some of these extensions change whole body of http request but I need to change a part of http request with regular expressions and submit modified request again. Please consider that body of http request is not static and we can only change a part of it and not whole of it. After some research I found that, this job can be done by proxy server. Briefly proxy server receives this http request, change required parameters and submit it again. Please let me know your solution. Best Regards,