How to save keypairs and send tokens in Solana, using node.js?

Question

I am attempting at using Solana over Ethereum for a particular solution.

I am using NPM to target Solana's API's. The packages being used are @solana/web3.js and @solana/spl-token. I've been able to create a successful connection and generate keypairs. I would like to be able to save a generated keypair, but the problem I face is that it's encoded, and the second issue to highlight is when I use the .toString(); it decodes it just fine but that can't be used in an airdrop.

const solanaWeb3 = require("@solana/web3.js"),
const solanatoken = require("@solana/spl-token");

(async () => {
  // Connect to cluster
  var connection = new solanaWeb3.Connection(
    solanaWeb3.clusterApiUrl("devnet"),
    "confirmed"
  );

  // Generate a new wallet keypair and airdrop SOL
  var wallet = solanaWeb3.Keypair.generate();
  console.log("public key...", wallet.publicKey)
  // The stringPK is an example of what wallet.publicKey returns. When taking wallet.publicKey and using .toString(); it returns the decoded publicKey but that can't be used in an airdrop.
  const stringPK = `_bn: <BN: e8a4421b46f76fdeac76819ab21708cc4a4b9c9c7fc2a22e373443539cee1a81>`;
  console.log("private key...", JSON.stringify(wallet.secretKey.toString()));
  console.log(solanaWeb3.PublicKey.decode(wallet.publicKey));
  var airdropSignature = await connection.requestAirdrop(
    stringPK,
    solanaWeb3.LAMPORTS_PER_SOL
  );

  //wait for airdrop confirmation
  await connection.confirmTransaction(airdropSignature);

  let account = await connection.getAccountInfo(wallet.publicKey);
  console.log(account);
})();

Answer 1

To save the generated keypair in JS, your best bet is to use secretKey on the Keypair object [1], write that to a file. To load it back up, you'll read that file and then use fromSecretKey to get back your Keypair [2]

As for your other issue, requestAirdrop takes a PublicKey, so instead, you should just do:

var airdropSignature = await connection.requestAirdrop(
    wallet.publicKey,
    solanaWeb3.LAMPORTS_PER_SOL
  );

[1] https://solana-labs.github.io/solana-web3.js/classes/Keypair.html#secretKey

[2] https://solana-labs.github.io/solana-web3.js/classes/Keypair.html#fromSecretKey