Mastering Blockchain Programming with Solidity

Using events for logging and callback

Solidity contracts do not have a way to generate logs when they are executed. Events are used to log values of the variables that can be listened as a callback by any JavaScript client. When events are emitted, its data is stored in the transaction's log.

Contracts emit event logs to let the other parties know that some action has been performed on the contract. Events also provide a way to maintain action history. Client applications can listen for the events as a callback and can take appropriate action when required. Client applications can also search for a specific event from the event history of the contract.

Deposited is an event in the following code, which is emitted when the deposit function ...