I am trying to connect to web3 1.0 through a web browser, I dont see much documentation for 1.0 though. This script says im connected but I think its the previous version as anytime I try and run a 1.0 function I get the function is undefined -

<script src="https://cdn.jsdelivr.net/gh/ethereum/[email protected]/dist/web3.min.js"></script>


function initweb3 () {
web3 = new Web3(new Web3.providers.HttpProvider("https://mainnet.infura.io/v3/My Api Key"));        


if(web3.isConnected()) {
    alert("Web3 Connected!");
} else {
    alert("Web3 Not Conected");

var abi = JSON.parse('[{"MY ABI"}]')

var AK = new web3.eth.contract(abi);

// Set Contract Address
AK.options.address = "Contract Address";

AK.methods.balanceOf("Address to get balance of").call().then(function(balance) { 
alert("Balance is " + balance.toString()) });

This Throws

 Uncaught TypeError: Cannot set property 'address' of undefined

It works fine when I run locally so I think its not connecting to version 1.0

2 Answers 2


I see that you found out a solution apparently. However the code proposed in the description of the problem is not correct and could have led to your error:

var AK = new web3.eth.contract(...)

Should actually be

var AK = new web3.eth.Contract(...)

Note the uppercase, which is necessary since you're actually instanciating a class here. This could have led to the undefined issue you faced. Furthermore, you can simplify your code (remove one line) by loading the contract at address directly:

var AK = new web3.eth.Contract(ABI, address)

This saves you one line. See the full documentation here.

  • yes you are correct, the lower case was for the older version and uppercase is needed for 1.0, I fixed this in my script but forgot to update it here.. Great catch!
    – Ryan D
    Oct 28, 2018 at 20:43

It works now

<script src="https://cdn.jsdelivr.net/gh/ethereum/[email protected]/dist/web3.min.js"></script>

var web3 = new Web3();
if(web3.setProvider(new Web3.providers.HttpProvider('https://mainnet.infura.io/v3/MY API KEY'))){

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