Classes are syntax over prototypes. They support a constructor, instance fields, methods, `static` members, private `#fields` and `extends` with `super`.
class Wallet {
#key;
constructor(address) { this.address = address; }
short() { return this.address.slice(0, 6); }
static zero() { return new Wallet("0x0"); }
}Methods live on the prototype and are shared; fields are per instance.