How would I do:

var GeneralizedSuffixArray = require('mnemonist/suffix-array').GeneralizedSuffixArray;
var suffixArray = new GeneralizedSuffixArray([
  'banana',
  'ananas'
]);

I would guess

(ns your-ns
  (:require ["mnemonist/suffix-array" :refer [GeneralizedSuffixArray]]))

(def suffix-array (GeneralizedSuffixArray. #js ["banana" "ananas"]))

This is a helpful reference for translating various import idioms to CLJS https://shadow-cljs.github.io/docs/UsersGuide.html#_using_npm_packages