Web Storage

Node hides sessionStorage and localStorage behind --experimental-webstorage on the 22.4–24 band (native from 25); Nub injects that flag on exactly that band. Below Node 22.4 the flag does not exist and Web Storage is unavailable.

sessionStorage

The sessionStorage global is in-memory and per-process: it is created fresh each run and discarded when the process exits.

sessionStorage.setItem("step", "1");
sessionStorage.getItem("step");      // "1"
sessionStorage.length;               // 1
sessionStorage.key(0);               // "step"
sessionStorage.removeItem("step");
sessionStorage.clear();

localStorage

The localStorage global persists across runs, so it needs a file on disk to write to. Pass --localstorage-file <path> and Nub forwards it to Node verbatim; until then localStorage is undefined, so typeof localStorage === "undefined" is a feature check.

localStorage.setItem("token", "abc123");
localStorage.getItem("token");        // "abc123"
localStorage.length;                  // 1
localStorage.key(0);                  // "token"
localStorage.removeItem("token");
localStorage.clear();

$ nub --localstorage-file=./app.db write.ts
abc123
$ nub --localstorage-file=./app.db read.ts
abc123

The --localstorage-file flag is also honored when set in NODE_OPTIONS.