pseudocode for a Non-Fungible Token smart contract (see ERC721 https://eips.ethereum.org/EIPS/eip-721)

NFT.js

// Global Token ID counter
Counter = 0

// Mapping from Token ID to user wallet address
Database = Map<int, address>{}

// Mint/create a NFT and assign it to a new wallet address
function CreateToken (ownerAddress) {
  // Limit so that only specific addresses can query this function
  // i.e. only the Artist can mint new tokens of this type
  if (Query.address != Distributor) throw "Only the Distributor can create a new Token"

  // Get a unique ID for the Token and increment global Counter
  id = Counter
  Counter += 1

  // Assign the unique Token ID to its new owner
  Database[id] = ownerAddress
}

// Query the wallet address that currently owns the specified Token ID
function OwnerOf (id) {
  return Database[id]
}

// Allow owner to transfer their token (NFT) from one wallet to another
function TransferToken (id, newOwnerAddress) {
  // Limit so that only the owner of that token can query this function
  if (Query.address != Database[id]) throw "Only the current Token Owner can transfer their Token"

  // Assign the Token ID to its new wallet address
  Database[id] = newOwnerAddress
}