ES import attributes (previously called import assertions) has been changed to use the with keyword. The old syntax using assert is still supported, but deprecated.

Invalid:

import obj from "./obj.json" assert { type: "json" };
import("./obj2.json", { assert: { type: "json" } });

Valid:

import obj from "./obj.json" with { type: "json" };
import("./obj2.json", { with: { type: "json" } });