How to Delegate Token Accounts

import {
  Connection,
  Keypair,
  Transaction,
  sendAndConfirmTransaction,
  SystemProgram,
  LAMPORTS_PER_SOL
} from "@solana/web3.js";
import {
  approveChecked,
  createApproveCheckedInstruction,
  revoke,
  createRevokeInstruction,
  createMint,
  getOrCreateAssociatedTokenAccount,
  createInitializeMintInstruction,
  createAssociatedTokenAccountInstruction,
  getAssociatedTokenAddress,
  MINT_SIZE,
  TOKEN_PROGRAM_ID
} from "@solana/spl-token";

(async () => {
  const connection = new Connection("http://127.0.0.1:8899", "confirmed");

  const tokenOwner = Keypair.generate();
  const airdropSignature = await connection.requestAirdrop(
    tokenOwner.publicKey,
    LAMPORTS_PER_SOL
  );
  await connection.confirmTransaction(airdropSignature);

  // Create delegate address
  const delegate = Keypair.generate();
  console.log(`Delegate pubkey: ${delegate.publicKey.toBase58()}`);

  // 1) Create mint using build-in function
  console.log("\n1. Creating mint using build-in function...");
  const mint = await createMint(
    connection,
    tokenOwner,
    tokenOwner.publicKey, // mint authority
    tokenOwner.publicKey, // freeze authority
    9 // decimals
  );
  console.log(`Mint created: ${mint.toBase58()}`);

  // 2) Create mint by composing transaction
  console.log("\n2. Creating mint by composing transaction...");
  const mintKeypair = Keypair.generate();
  const mintRent =
    await connection.getMinimumBalanceForRentExemption(MINT_SIZE);

  const createMintTx = new Transaction().add(
    // Create account for mint
    SystemProgram.createAccount({
      fromPubkey: tokenOwner.publicKey,
      newAccountPubkey: mintKeypair.publicKey,
      space: MINT_SIZE,
      lamports: mintRent,
      programId: TOKEN_PROGRAM_ID
    }),
    // Initialize mint
    createInitializeMintInstruction(
      mintKeypair.publicKey,
      9, // decimals
      tokenOwner.publicKey, // mint authority
      tokenOwner.publicKey // freeze authority
    )
  );

  console.log(
    `Create mint txhash: ${await sendAndConfirmTransaction(
      connection,
      createMintTx,
      [tokenOwner, mintKeypair]
    )}`
  );

  // 3) Create token account using build-in function
  console.log("\n3. Creating token account using build-in function...");
  const tokenAccount = await getOrCreateAssociatedTokenAccount(
    connection,
    tokenOwner,
    mint, // mint
    tokenOwner.publicKey // owner
  );
  console.log(`Token account created: ${tokenAccount.address.toBase58()}`);

  // 4) Create token account by composing transaction
  console.log("\n4. Creating token account by composing transaction...");
  const associatedTokenAddress = await getAssociatedTokenAddress(
    mintKeypair.publicKey, // mint
    tokenOwner.publicKey // owner
  );

  const createTokenAccountTx = new Transaction().add(
    createAssociatedTokenAccountInstruction(
      tokenOwner.publicKey, // payer
      associatedTokenAddress, // token address
      tokenOwner.publicKey, // owner
      mintKeypair.publicKey // mint
    )
  );

  console.log(
    `Create token account txhash: ${await sendAndConfirmTransaction(
      connection,
      createTokenAccountTx,
      [tokenOwner]
    )}`
  );

  // Use the created mint and token account for delegation
  const mintPubkey = mint;
  const tokenAccountPubkey = tokenAccount.address;

  // 5) Approve delegation using build-in function
  {
    console.log("\n5. Approving delegation with specific amount...");
    const txhash = await approveChecked(
      connection,
      tokenOwner,
      mintPubkey,
      tokenAccountPubkey,
      delegate.publicKey,
      tokenOwner,
      500000000,
      9
    );
    console.log(`Approve delegation txhash: ${txhash}`);
  }

  // 6) Approve delegation by composing transaction
  {
    console.log("\n2. Approving delegation by composing transaction...");
    const tx = new Transaction().add(
      createApproveCheckedInstruction(
        tokenAccountPubkey, // token account
        mintPubkey, // mint
        delegate.publicKey, // delegate
        tokenOwner.publicKey, // owner of token account
        500000000, // amount, if your decimals is 9, 0.5 tokens
        9 // decimals
      )
    );
    console.log(
      `Approve delegation txhash: ${await sendAndConfirmTransaction(
        connection,
        tx,
        [tokenOwner]
      )}`
    );
  }
})();