todo.txt

Add transaction fees into each transaction.

Instead of using pending transactions array for mining, compute merkel root.

Declare API callback functions in separate file so that they can be used internally as well.

After registering and broadcasting a new network node, send the entire blockchain to the new node as well. (For this consensus algorithm can be used)

Use typescript for strict type checks and better security/error handling.

Store the blockchain data in some kind of data storage so that it's not lost on server restart. Maybe redis or mongo.

Use lodash for checking empty values and other utilities for better edge cases coverage.

Call consensus on a new node when it's registered on the network.

Enhance blockchain explorer. By default show entire blockchain. Have search in a different tab. Try to make a common search.

Check for available balance with the sender before creating a new transaction.