What are the levels of transaction isolation in database management systems?

In database management systems (DBMS), there are four main transaction isolation levels that define how one transaction is visible to others:

1. Read Uncommitted — the lowest level, where a transaction may see uncommitted changes made by others (dirty reads).
2. Read Committed — a transaction only sees committed changes. Prevents dirty reads but non-repeatable reads are possible.
3. Repeatable Read — guarantees that if a transaction reads data, it will see the same data if it reads again within the same transaction. Prevents non-repeatable reads but phantom reads are possible.
4. Serializable — the strictest level, transactions are executed as if serially, preventing all anomalies but reducing concurrency.

In Node.js, when working with databases via drivers or ORM, you can usually specify the transaction isolation level when beginning a transaction.