When we use EMACS/Spacemacs and want to use two repls for CLJ and CLJS then
1. just add (add-to-list 'auto-mode-alist '("\.cljs$" . clojurescript-mode)) to init.el to enable clojurescript-mode for cljs files (otherwise it will be clojure mode with some problems in CLJS).
2. Select CLJ file and run cider-jack-in to run Clojure REPL
3. Select CLJS file (check that EMACS in Clojurescript mode) and run cider-jack-in-clojurescript or run cider-jack-in and then (require'[ figwheel-sidecar.repl-api :as f]) and
(f/start-figwheel!) and (f/cljs-repl)
If I need to work with two different Clojure REPLs and eval S-forms I do following.
Run two REPLs by cider-jack-in command.
To switch between REPL connections:
1. M-x and choose cider-toogle-request-dispatch to set CIDER variable to static mode
2. choose appropriate repl window and run command: cider-make-connection-default
Now, all S-exp will be evaluated in a default repl process.