How to get the price of MATIC token using infura and web3.js?

Question

I have written the following code:

const web3 = new Web3(
            'https://polygon-mainnet.infura.io/v3/<INFURA_PROJECT_ID>'
        )
        const aggregatorV3InterfaceABI = [{ "inputs": [], "name": "decimals", "outputs": [{ "internalType": "uint8", "name": "", "type": "uint8" }], "stateMutability": "view", "type": "function" }, { "inputs": [], "name": "description", "outputs": [{ "internalType": "string", "name": "", "type": "string" }], "stateMutability": "view", "type": "function" }, { "inputs": [{ "internalType": "uint80", "name": "_roundId", "type": "uint80" }], "name": "getRoundData", "outputs": [{ "internalType": "uint80", "name": "roundId", "type": "uint80" }, { "internalType": "int256", "name": "answer", "type": "int256" }, { "internalType": "uint256", "name": "startedAt", "type": "uint256" }, { "internalType": "uint256", "name": "updatedAt", "type": "uint256" }, { "internalType": "uint80", "name": "answeredInRound", "type": "uint80" }], "stateMutability": "view", "type": "function" }, { "inputs": [], "name": "latestRoundData", "outputs": [{ "internalType": "uint80", "name": "roundId", "type": "uint80" }, { "internalType": "int256", "name": "answer", "type": "int256" }, { "internalType": "uint256", "name": "startedAt", "type": "uint256" }, { "internalType": "uint256", "name": "updatedAt", "type": "uint256" }, { "internalType": "uint80", "name": "answeredInRound", "type": "uint80" }], "stateMutability": "view", "type": "function" }, { "inputs": [], "name": "version", "outputs": [{ "internalType": "uint256", "name": "", "type": "uint256" }], "stateMutability": "view", "type": "function" }]
        const addr = '0xAB594600376Ec9fD91F8e885dADF0CE036862dE0'
        const priceFeed = web3.eth.contract(aggregatorV3InterfaceABI, addr)

        priceFeed.methods
            .latestRoundData()
            .call()
            .then((roundData) => {
                console.log(roundData.answer);
            })

I'm using the Infura API to talk to smart contracts on the Polygon mainnet.

However, I'm getting the following error on console:

Uncaught TypeError: Cannot read properties of undefined (reading 'latestRoundData')

My libraries and their versions are as follows:

> web3.js : 0.19.0
> Truffle : v5.4.32
> truffle-contract.min.js : 4.0.31

Answer 1

The following code works fine to me. I believe your mistake was in the declarationn -> const priceFeed = web3.eth.contract(aggregatorV3InterfaceABI, addr). See mine below.

import Web3 from 'web3'

async function run() {

const web3 = new Web3(
    'https://polygon-mainnet.infura.io/v3/d34f69843c144d3ab51b1915ff36260e'
)
const aggregatorV3InterfaceABI = [{ "inputs": [], "name": "decimals", "outputs": [{ "internalType": "uint8", "name": "", "type": "uint8" }], "stateMutability": "view", "type": "function" }, { "inputs": [], "name": "description", "outputs": [{ "internalType": "string", "name": "", "type": "string" }], "stateMutability": "view", "type": "function" }, { "inputs": [{ "internalType": "uint80", "name": "_roundId", "type": "uint80" }], "name": "getRoundData", "outputs": [{ "internalType": "uint80", "name": "roundId", "type": "uint80" }, { "internalType": "int256", "name": "answer", "type": "int256" }, { "internalType": "uint256", "name": "startedAt", "type": "uint256" }, { "internalType": "uint256", "name": "updatedAt", "type": "uint256" }, { "internalType": "uint80", "name": "answeredInRound", "type": "uint80" }], "stateMutability": "view", "type": "function" }, { "inputs": [], "name": "latestRoundData", "outputs": [{ "internalType": "uint80", "name": "roundId", "type": "uint80" }, { "internalType": "int256", "name": "answer", "type": "int256" }, { "internalType": "uint256", "name": "startedAt", "type": "uint256" }, { "internalType": "uint256", "name": "updatedAt", "type": "uint256" }, { "internalType": "uint80", "name": "answeredInRound", "type": "uint80" }], "stateMutability": "view", "type": "function" }, { "inputs": [], "name": "version", "outputs": [{ "internalType": "uint256", "name": "", "type": "uint256" }], "stateMutability": "view", "type": "function" }]
const addr = '0xAB594600376Ec9fD91F8e885dADF0CE036862dE0'
const priceFeed = new web3.eth.Contract(aggregatorV3InterfaceABI, addr)

priceFeed.methods
    .latestRoundData()
    .call()
    .then((roundData) => {
        console.log(roundData.answer);
    })
}

run()