parseEventLogs

Extracts & decodes logs matching the provided abi (and optional eventName) from a set of opaque logs.

Useful for decoding logs on Transaction Receipts.

Install

import { parseEventLogs } from 'viem'

Usage

example.ts

import { parseEventLogs } from 'viem'
import { erc20Abi } from './abi'
import { client } from './client'
 
const receipt = await getTransactionReceipt(client, {
  hash: '0xec23b2ba4bc59ba61554507c1b1bc91649e6586eb2dd00c728e8ed0db8bb37ea',
})
 
const logs = parseEventLogs({ 
  abi: erc20Abi, 
  logs: receipt.logs,
})
// [
//   { args: { ... }, eventName: 'Transfer', logIndex: 3 ... },  
//   { args: { ... }, eventName: 'Approval', logIndex: 5 ... },
//   ...
// ]

Scoping to Event Name(s)

You can scope the logs to a specific event name by providing the eventName argument:

example.ts

import { parseEventLogs } from 'viem'
import { erc20Abi } from './abi'
import { client } from './client'
 
const receipt = await getTransactionReceipt(client, {
  hash: '0xec23b2ba4bc59ba61554507c1b1bc91649e6586eb2dd00c728e8ed0db8bb37ea',
})
 
const logs = parseEventLogs({ 
  abi: erc20Abi, 
  eventName: 'Transfer', 
  logs: receipt.logs,
})
// [
//   { args: { ... }, eventName: 'Transfer', logIndex: 3, ... },  
//   { args: { ... }, eventName: 'Transfer', logIndex: 7, ... },
//   ...
// ]

You can also pass an array to scope multiple event names:

example.ts

import { parseEventLogs } from 'viem'
import { erc20Abi } from './abi'
import { client } from './client'
 
const receipt = await getTransactionReceipt(client, {
  hash: '0xec23b2ba4bc59ba61554507c1b1bc91649e6586eb2dd00c728e8ed0db8bb37ea',
})
 
const logs = parseEventLogs({ 
  abi: erc20Abi, 
  eventName: ['Transfer', 'Approval'], 
  logs: receipt.logs,
})
// [
//   { args: { ... }, eventName: 'Transfer', logIndex: 3, ... },  
//   { args: { ... }, eventName: 'Approval', logIndex: 5, ... },  
//   { args: { ... }, eventName: 'Transfer', logIndex: 7, ... },
//   ...
// ]

Partial Decode

By default, if the topics and data does not conform to the ABI (a mismatch between the number of indexed/non-indexed arguments), parseEventLogs will not return return the decoded log.

For example, the following will not return the nonconforming log as there is a mismatch in non-indexed arguments & data length.

parseEventLogs({
  abi: parseAbi(['event Transfer(address indexed, address, uint256)']),
  logs: [{
    // `data` should be 64 bytes, but is only 32 bytes.
    data: '0x0000000000000000000000000000000000000000000000000000000000000001', 
    topics: [
      '0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef',
      '0x000000000000000000000000f39fd6e51aad88f6f4ce6ab8827279cfffb92266',
    ]
    // ...
  }]
})
// []

It is possible for parseEventLogs to try and partially decode the Log, this can be done by setting the strict argument to false:

parseEventLogs({
  abi: parseAbi(['event Transfer(address indexed, address, uint256)']),
  logs: [{
    data: '0x0000000000000000000000000000000000000000000000000000000000000001',
    topics: [
      '0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef',
      '0x000000000000000000000000f39fd6e51aad88f6f4ce6ab8827279cfffb92266',
    ]
    // ...
  }]
  strict: false
})
/**
 * [
 *  {
 *    eventName: 'Transfer',
 *    args: ['0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266'],
 *    blockNumber: 42069420n,
 *    logIndex: 69,
 *    ...
 *  }
 * ]
 */

Return Value

Log[]

Decoded logs.

Parameters

abi

Type: Abi

The contract's ABI.

const topics = parseEventLogs({
  abi: wagmiAbi, 
  logs: [{
    blockNumber: 69420n,
    data: '0x0000000000000000000000000000000000000000000000000000000000000001',
    logIndex: 1,
    topics: [
      '0x406dade31f7ae4b5dbc276258c28dde5ae6d5c2773c5745802c493a2360e55e0', 
      '0x00000000000000000000000000000000f39fd6e51aad88f6f4ce6ab8827279cfffb92266', 
      '0x0000000000000000000000000000000070997970c51812dc3a010c7d01b50e0d17dc79c8'
    ]
    // ...
  }]
})

logs

Type: Log[]

An array of logs to parse.

const topics = parseEventLogs({
  abi: wagmiAbi,
  logs: [{ 
    blockNumber: 69420n, 
    data: '0x0000000000000000000000000000000000000000000000000000000000000001', 
    logIndex: 1, 
    topics: [ 
      '0x406dade31f7ae4b5dbc276258c28dde5ae6d5c2773c5745802c493a2360e55e0',  
      '0x00000000000000000000000000000000f39fd6e51aad88f6f4ce6ab8827279cfffb92266', 
      '0x0000000000000000000000000000000070997970c51812dc3a010c7d01b50e0d17dc79c8'
    ] 
    // ...
  }] 
})

eventName (optional)

Type: string

An event name from the ABI.

const topics = parseEventLogs({
  abi: wagmiAbi,
  eventName: 'Transfer', 
  logs: [{
    blockNumber: 69420n,
    data: '0x0000000000000000000000000000000000000000000000000000000000000001',
    logIndex: 1,
    topics: [
      '0x406dade31f7ae4b5dbc276258c28dde5ae6d5c2773c5745802c493a2360e55e0', 
      '0x00000000000000000000000000000000f39fd6e51aad88f6f4ce6ab8827279cfffb92266', 
      '0x0000000000000000000000000000000070997970c51812dc3a010c7d01b50e0d17dc79c8'
    ]
    // ...
  }]
})

strict (optional)

Type: boolean
Default: true

If true, parseEventLogs will not return nonconforming logs. If false, parseEventLogs will try and partially decode nonconforming logs.

const topics = parseEventLogs({
  abi: wagmiAbi,
  eventName: 'Transfer',
  logs: [{
    blockNumber: 69420n,
    data: '0x0000000000000000000000000000000000000000000000000000000000000001',
    logIndex: 1,
    topics: [
      '0x406dade31f7ae4b5dbc276258c28dde5ae6d5c2773c5745802c493a2360e55e0', 
      '0x00000000000000000000000000000000f39fd6e51aad88f6f4ce6ab8827279cfffb92266', 
      '0x0000000000000000000000000000000070997970c51812dc3a010c7d01b50e0d17dc79c8'
    ]
    // ...
  }],
  strict: false
})