Advanced

Example Block Functions

Block functions are JavaScript transformation functions that enable you to filter the data included in a stream. This page outlines some example functions to illustrate how you can improve efficiency by streaming only the data that you require.

Stream specific values

This example function specifies that Project Zero only streams the following for each block:

  • The block number, as an integer
  • The timestamp, as a human-readable string
  • The hash
  • The previous hash
function main(block) {
  return {
    number: parseInt(block.number, 16),
    time: new Date(parseInt(block.timestamp, 16) * 1_000).toISOString(),
    hash: block.hash,
    parentHash: block.parentHash,
  };
}

The following files show example data for three blocks and demonstrate how this function transforms that data:

Stream specific log events

This example function specifies that Project Zero only streams logs for the following events on the Uniswap V3 protocol:

  • Swap
  • Mint
  • Burn
  • Flash
  • Collect
const poolEventSignatures = new Map([
  ['0xc42079f94a6350d7e6235f29174924f928cc2ac818eb64fed8004e115fbcca67', 'Swap'],
  ['0x7a53080ba414158be7ec69b987b5fb7d07dee101fe85488f0853ae16239d0bde', 'Mint'],
  ['0x0c396cd989a39f4459b5fa1aed6a9a8dcdbc45908acfd67e028cd568da98982c', 'Burn'],
  ['0xbdbdb71d7860376ba52b25a5028beea23581364a40522f6bcfb86bb1f2dca633', 'Flash'],
  ['0x70935338e69775456a85ddef226c395fb668b63fa0115f5f20610b388e6ca9c0', 'Collect'],
]);
const factoryFoolCreatedSignature = '0x783cca1c0412dd0d695e784568c96da2e9c22ff989357a2e8b1d9b2b4e6b7118';
 
function isUniswapV3Log(item) {
  if (item.topics[0] === factoryFoolCreatedSignature && item.address === '0x1f98431c8ad98523631ae4a59f267346ea31f984') {
    return true;
  }
 
  return poolEventSignatures.has(item.topics[0]);
}
 
function main(block) {
  return _.filter(block, isUniswapV3Log);
}

In this second example, the following files show example data for three blocks and demonstrate how this function transforms that data:

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