Should I use Service Callout or javascript to do a conditional mashup

[#1]

I have a mashup use case where I'm calling n-number backend Apis based on query parameter value

For instance, if the request comes to https://my-api?include=service1,service2, service3 I would then need to call all three backend Apis. However, if they only included service1,service3 I would only call two APIs.

For a usecase like this, which of these is recommended and what drives the recommendation

1. Service Callouts with Regex condition
2. Javascript
3. Node.js