LIGHTWEIGHT TEMPLATES
Yes. JavaScript callbacks like showOffer and showTemplate work for Lightweight Templates the same way they do for Classic templates. You can register handlers using tp.push(["addHandler", ...]) as you normally would:
tp.push(["addHandler", "showTemplate", () => {
console.log('showTemplate');
}]);
tp.push(["addHandler", "showOffer", () => {
console.log('showOffer');
}]);
No changes are required when migrating from Classic to Lightweight — existing handler registrations continue to function without modification.