How to pay rent fee when creating solana wallet in nodejs - node.js

Question

hello I create solana wallet with the following code on my nodejs server.
const SolanaWeb3 = require("#solana/web3.js");
SolanaWeb3.Keypair.generate();
I don't think this is an active wallet. Because I haven't paid the rent fee for this account.
**So I want to know when is the moment when this inactive account pays the rent fee.
(I want to know if it is activated when a transaction in which sol is deposited into this account occurs, or whether this account should generate a transaction that sends solana to another place.)
And I want to know if there is a javascript function that gives rent fee when account is created.**
thank you for your reply.

Answer 1

To your second question
And I want to know if there is a javascript function that gives rent fee when account is created
Yes there is. Assuming you just want a system account that holds SOL versus an account that has data:
// amount of space to reserve for the account. system accounts are 0 space
const space = 0;
// Get the rent, in lamports, for exemption
const rentExemptionAmount =
await connection.getMinimumBalanceForRentExemption(space);
To your first question
If you already have a funded account (fromKeyPair), you can use that accounts public key to fund the new account you want to create:
const newAccountKeypair = SolanaWeb3.Keypair.generate();
const createAccountParams = {
fromPubkey: fromKeyPair.publicKey,
newAccountPubkey: newAccountKeypair.publicKey,
lamports: rentExemptionAmount,
space,
programId: SolanaWeb3.SystemProgram.programId,
};
const createAccountTransaction = new SolanaWeb3.Transaction().add(
SolanaWeb3.SystemProgram.createAccount(createAccountParams)
);
await SolanaWeb3.sendAndConfirmTransaction(connection, createAccountTransaction, [
fromKeyPair,
newAccountKeypair,
]);