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Overview

Event.encodeTopics builds the topics array for an event filter. It includes topic0 (the event selector) for non-anonymous events and encodes indexed parameters as topics.

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Quick Start

import { Abi } from '@tevm/voltaire/Abi';
import { Hex } from '@tevm/voltaire/Hex';

const Transfer = {
  type: 'event',
  name: 'Transfer',
  inputs: [
    { type: 'address', name: 'from', indexed: true },
    { type: 'address', name: 'to', indexed: true },
    { type: 'uint256', name: 'value' }
  ]
} as const;

const topics = Abi.Event.encodeTopics(Transfer, {
  from: '0x742d35Cc6634C0532925a3b844Bc9e7595f51e3e',
  to: '0x5B38Da6a701c568545dCfcB03FcB875f56beddC4'
});

const topicHex = topics.map((t) => (t ? Hex.fromBytes(t) : null));

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Wildcards and Partial Filters

Set an indexed value to null (or omit it) to leave that topic unconstrained: 
const topics = Abi.Event.encodeTopics(Transfer, {
  from: null,
  to: '0x5B38Da6a701c568545dCfcB03FcB875f56beddC4'
});

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Use in Log Filters

encodeTopics returns byte arrays. Convert to hex strings when passing to JSON-RPC: 
const topics = Abi.Event.encodeTopics(Transfer, {
  from: null,
  to: '0x5B38Da6a701c568545dCfcB03FcB875f56beddC4'
});

const filterTopics = topics.map((t) => (t ? Hex.fromBytes(t) : null));

const logs = await provider.getLogs({
  address: tokenAddress,
  topics: filterTopics
});

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Dynamic Indexed Parameters

Dynamic types (string, bytes, dynamic arrays, tuples with dynamic parts) are hashed with keccak256 before being placed in a topic. You cannot recover the original value from the topic alone.

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Anonymous Events

Anonymous events omit topic0. encodeTopics will return only the indexed parameter topics.

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See Also