NFT Frontend Minting and Integration 2 — Questions and Answers
Question 1: In a React dApp, which library function is most commonly used to connect a browser wallet via injected providers like MetaMask?
- window.ethereum.request({ method: 'eth_requestAccounts' }) (Correct answer)
- fetch('/connect')
- localStorage.getItem('wallet')
- navigator.connectWallet()
Correct answer: window.ethereum.request({ method: 'eth_requestAccounts' })
EIP-1193 providers expose window.ethereum, and eth_requestAccounts prompts the user to connect their accounts.
Question 2: When minting an NFT from the frontend, why should the total mint cost (price × quantity) be sent in the transaction's 'value' field?
- The contract's payable mint function requires ETH to cover the price (Correct answer)
- It sets the gas limit
- It encrypts the transaction
- It registers the user's email
Correct answer: The contract's payable mint function requires ETH to cover the price
A payable mint function expects msg.value to equal the required payment, so the value field must carry the ETH.
Question 3: What is the purpose of listening to a contract's 'Transfer' event after a mint transaction confirms on the frontend?
- To detect the newly minted tokenId and update the UI (Correct answer)
- To pay gas fees
- To deploy the contract
- To compile Solidity
Correct answer: To detect the newly minted tokenId and update the UI
The Transfer event from the zero address signals a mint and exposes the new tokenId for UI updates.
Question 4: Which approach prevents a user from being charged for a failed mint when the sale is paused on-chain?
- Call a read-only view (e.g., saleActive) before sending the transaction (Correct answer)
- Increase the gas limit
- Send the transaction twice
- Disable JavaScript
Correct answer: Call a read-only view (e.g., saleActive) before sending the transaction
Reading the sale state first lets the UI block transactions that would revert, saving the user gas.
Question 5: In ethers.js v6, what does a 'Contract' instance need to send a state-changing mint transaction rather than just read data?
- A signer connected to the contract (Correct answer)
- Only a JSON-RPC provider
- A private key hardcoded in the frontend
- An Infura API key in the HTML
Correct answer: A signer connected to the contract
Read calls work with a provider, but write transactions require a signer that can authorize and submit them.
Question 6: Why is it risky to display 'mint successful' immediately after calling the contract method without awaiting the receipt?
- The transaction may still revert or be dropped before confirmation (Correct answer)
- It uses too much memory
- It violates CORS
- It changes the chainId
Correct answer: The transaction may still revert or be dropped before confirmation
A submitted transaction can still fail or be dropped, so success should only show after the receipt confirms.
Question 7: What does the EIP-1193 'chainChanged' event allow a dApp frontend to do?
- Detect when the user switches networks and refresh or reload state (Correct answer)
- Mint tokens automatically
- Sign the user out of MetaMask
- Lower gas prices
Correct answer: Detect when the user switches networks and refresh or reload state
Listening for chainChanged lets the dApp react to network switches, often by reloading to avoid stale state.
NFT Frontend Minting and Integration 2
In a React dApp, which library function is most commonly used to connect a browser wallet via injected providers like MetaMask?