encodeEventTopics
Encodes an event (with optional arguments) into filter topics.
Install
ts
import { encodeEventTopics } from 'viem'
Usage
Below is a very basic example of how to encode event topics without arguments.
ts
import { encodeEventTopics } from 'viem'
const topics = encodeEventTopics({
abi: wagmiAbi,
eventName: 'Transfer'
})
// ["0x406dade31f7ae4b5dbc276258c28dde5ae6d5c2773c5745802c493a2360e55e0"]
ts
export const wagmiAbi = [
...
{
inputs: [
{
indexed: true,
name: 'from',
type: 'address',
},
{ indexed: true, name: 'to', type: 'address' },
{
indexed: false,
name: 'value',
type: 'uint256',
},
],
name: 'Transfer',
type: 'event',
},
...
] as const;
ts
import { createPublicClient, http } from 'viem'
import { mainnet } from 'viem/chains'
export const publicClient = createPublicClient({
chain: mainnet,
transport: http()
})
Passing Arguments
If your event has indexed parameters, you can pass their values through with the args attribute.
TypeScript types for args will be inferred from the event name & ABI, to guard you from inserting the wrong values.
For example, the Transfer event below accepts an address argument for the from and to attributes, and it is typed as "0x${string}".
ts
import { encodeEventTopics } from 'viem'
const topics = encodeEventTopics({
abi: wagmiAbi,
eventName: 'Transfer'
args: {
from: '0xf39fd6e51aad88f6f4ce6ab8827279cfffb92266',
to: '0x70997970c51812dc3a010c7d01b50e0d17dc79c8'
}
})
// ["0x406dade31f7ae4b5dbc276258c28dde5ae6d5c2773c5745802c493a2360e55e0", "0x00000000000000000000000000000000f39fd6e51aad88f6f4ce6ab8827279cfffb92266", "0x0000000000000000000000000000000070997970c51812dc3a010c7d01b50e0d17dc79c8"]
ts
export const wagmiAbi = [
...
{
inputs: [
{
indexed: true,
name: 'from',
type: 'address',
},
{ indexed: true, name: 'to', type: 'address' },
{
indexed: false,
name: 'value',
type: 'uint256',
},
],
name: 'Transfer',
type: 'event',
},
...
] as const;
ts
import { createPublicClient, http } from 'viem'
import { mainnet } from 'viem/chains'
export const publicClient = createPublicClient({
chain: mainnet,
transport: http()
})
Without eventName
If your abi contains only one ABI item, you can omit the eventName (it becomes optional):
ts
import { encodeEventTopics } from 'viem'
const abiItem = {
inputs: [
{
indexed: true,
name: 'from',
type: 'address',
},
{ indexed: true, name: 'to', type: 'address' },
{
indexed: false,
name: 'value',
type: 'uint256',
},
],
name: 'Transfer',
type: 'event',
}
const topics = encodeEventTopics({
abi: [abiItem],
eventName: 'Transfer'
})
// ["0x406dade31f7ae4b5dbc276258c28dde5ae6d5c2773c5745802c493a2360e55e0"]
Return Value
Encoded topics.
Parameters
abi
- Type:
Abi
The contract's ABI.
ts
const data = encodeEventTopics({
abi: wagmiAbi,
functionName: 'Transfer',
})
eventName
- Type:
string
Name of the event.
ts
const data = encodeEventTopics({
abi: wagmiAbi,
eventName: 'Transfer',
})
args (optional)
- Type:
string
A list of indexed event arguments.
ts
const data = encodeEventTopics({
abi: wagmiAbi,
eventName: 'Transfer',
args: {
from: '0xd8da6bf26964af9d7eed9e03e53415d37aa96045',
to: '0xa5cc3c03994db5b0d9a5eedd10cabab0813678ac'
}
})