How to use getProgramAccounts to filter a JS number?

Question

I want to get all the program accounts with a filter. The variable country is a number in my code and I don't know how to convert it to bytes for the filtering to work.

const country = 0;

const sellerAccountFilters = {
  filters: [
        {
          dataSize: 198,
        },
        {
          memcmp: {
            offset: 8,
            // How to convert country from number to bytes ?
            bytes: country,
          },
        },
      ],
    };

const sellerAccount = await connection.getProgramAccounts(programID,filters);

Thanks in advance,

Answer 1

The memcmp bytes are expected to be a base-58 representation of the data to be compared. For numerical data comparisons, you can convert the number of base-58 with:

import bs58 from 'bs58'

const country = 0
const sellerAccountFilters = {
  filters: [
    {
      dataSize: 198,
    },
    {
      memcmp: {
        offset: 8,
        bytes: bs58.encode(Buffer.from([country])),
      },
    },
  ],
};

With country being 0, this should correctly encode the buffer as '1' in base-58.