I created a smart contract (lets call it MyContract) and deployed it on Mumbai testnet. I used this tutorial to connect to MyContract. this is my code:

import maticjs from '@maticnetwork/maticjs';
const { POSClient,use } = maticjs;
import maticjsWeb3 from '@maticnetwork/maticjs-web3';
const { Web3ClientPlugin } = maticjsWeb3;
import HDWalletProvider from "@truffle/hdwallet-provider";
import * as dotenv from 'dotenv'

// install web3 plugin

const posClient = new POSClient();

let fromAddress = "<my private address (also the miner of the contract)>";

await posClient.init({
    network: 'testnet',
    version: 'mumbai',
    parent: {
      provider: new HDWalletProvider(process.env.MNEMONIC, process.env.MUMBAI_RPC_URL)
    child: {
      provider: new HDWalletProvider(process.env.MNEMONIC, process.env.MUMBAI_RPC_URL),
      defaultConfig: {
        from : fromAddress

const erc20ChildToken = posClient.erc20("<MyContract address>");

const balance = await erc20ChildToken.getBalance(fromAddress);
console.log('balance', balance/10**18);

const result = await erc20ChildToken.stake(10);
console.log('result ', result)

as you can see in the last 2 rows I have a call erc20ChildToken.stake by which I intended to call the stake function of the contract, but I get this error:

TypeError: erc20ChildToken.stake is not a function

How can I access "special" functions that are not part of the standard ERC20 interface?

1 Answer 1


You need to provide the correct ABI and create a contract with it. You can also use a low-level call but the better way is with the correct ABI.

  • how do I do that? can you share a code example? or maybe a guide online? haven't found anything good when I searched
    – orr
    Oct 20, 2022 at 6:46
  • Do you want it specific to maticJS or you don’t mind?
    – matank001
    Oct 20, 2022 at 7:49
  • I don't mind, as long as it works for polygon
    – orr
    Oct 23, 2022 at 6:33

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