Ethereum Developer Web3.js, Ethers.js and Ethereum APIs 2

Question 1

What does `eth_call` do in contrast to `eth_sendTransaction`?

Accepted Answer

eth_call simulates a call without modifying state; eth_sendTransaction writes to the chain

Answer

`eth_call` executes a function locally without creating a transaction, while `eth_sendTransaction` broadcasts a state-changing transaction.

Question 2

What is the unit `Wei` in Ethereum?

Accepted Answer

The smallest denomination of Ether (1 ETH = 10^18 Wei)

Answer

Wei is the smallest indivisible unit of Ether, with 1 ETH equal to 1,000,000,000,000,000,000 (10^18) Wei.

Question 3

What is an Ethereum event filter used for in ethers.js?

Accepted Answer

To listen for and query specific smart contract events emitted on-chain

Answer

Event filters in ethers.js allow developers to subscribe to or query specific contract events by topic and address.

Question 4

What does the `nonce` in an Ethereum transaction represent?

Accepted Answer

The number of transactions sent from the sender's address, used to order and deduplicate transactions

Answer

The nonce is a sequential counter for each account ensuring transactions execute in order and preventing replay attacks.

Question 5

What is the purpose of `eth_getLogs` in Ethereum's JSON-RPC API?

Accepted Answer

To retrieve historical event logs matching a given filter

Answer

`eth_getLogs` returns an array of log objects matching the specified filter (address, topics, block range) from the blockchain.

Ethereum Developer Practice Test