I have a Solidity function:

    function add(uint256 a, uint256 b) public pure returns (uint256) {
        uint256 result = a + b;
        return result;

That I've migrated over to Solana using solang. I want to call the add() function in a NodeJS script. It seems I need to serialize the call using the borsh serializer package.

The problem I have is that I can't figure out how to create the required schema for this Solana transaction instruction object:

   const num1 = 10;
   const num2 = 20;
   const transcationInstruction = {
      add: {

For what it's worth, I am trying to follow this example from from the GitHub page. But, I can't quite grasp how to serialize a nested JSON object.

The end goal is I want to define a transaction instruction like so:

  const instruction = new TransactionInstruction({
    keys: [
      { pubkey: payerKeypair.publicKey, isSigner: true },
      { pubkey: programAccountId, isSigner: false },
    programId: programAccountId,
    data: encodedInstruction,


encodedInstruction is the borsh serialized transaction instruction for the add(num1, num2) function in the Solana smart contract.

Thus, I reach out for help. Thanks in advance for any assistance.

I owe you one.

1 Answer 1


Typically an instruction is serialized as an enum, ie:

const schema = { enum: [{ struct: { add: { struct: { num1: 'u64', num2: 'u64' } }}}] };

Which you can serialize by running:

const encoded = borsh.serialize(schema, {add: { num1: 10, num2: 20 } });

This is according to the examples in the README. In your program you should double-check that the bytes are correct.

  • Thank you @Jon C! Will try your suggestion today!
    – reselbob
    Commented Dec 12, 2023 at 21:03

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