Modify schema in transaction?

I’m using the JavaScript gRPC client, and I’m familiar with the example for altering the database…

const schema = "name: string @index(exact) .";
const op = new dgraph.Operation();
await dgraphClient.alter(op);

…but is it possible to modify the schema in a transaction, so I can abort if needed and not have any schema changes take effect?

Nope, as far as I know. Alter Schema is an operation.