getBalance of shows the wrong balance

Question

I have this code to show the erc20 token balance of an account

   var tokenAddress = '0xb97E9bBB6fd49865709d3F1576e8506ad640a13B';
var walletAddress = '0x62f28320f688A7A4e0021c55d7ffD1acd770A133';



    function getERC20TokenBalance() {

      let minABI = [
        // balanceOf
        {
          "constant":true,
          "inputs":[{"name":"_owner","type":"address"}],
          "name":"balanceOf",
          "outputs":[{"name":"balance","type":"uint256"}],
          "type":"function"
        },
        // decimals
        {
          "constant":true,
          "inputs":[],
          "name":"decimals",
          "outputs":[{"name":"","type":"uint8"}],
          "type":"function"
        }
      ];


      let contract2 = web3.eth.contract(minABI).at(tokenAddress);

      web3.eth.getAccounts(function (error, walletAddress) {
          contract2.balanceOf(walletAddress, function(err, result) {
              if(err) {
                  console.log(err, 'err');
              } else {
                console.log(result);
                  document.getElementById('agiAvailable').innerHTML = result + ' AGI';

              }
          });
      });
    }
    getERC20TokenBalance();

    function onAddressChange(e) {

      if(tokenAddress != "" && walletAddress != "") {
        getERC20TokenBalance(tokenAddress, walletAddress, (balance) => {
          console.log(balance.toString());
        });
      }
    }

But that output is 0, which is not the correct balance

Answer 1

I hope that this will answer your question:

walletAddress = '0x62f28320f688A7A4e0021c55d7ffD1acd770A133' → walletAddress[0] = '0'.

And when you call contract2.balanceOf(walletAddress[0]), web3 most likely converts that '0' into the zero address 0x0000000000000000000000000000000000000000', whose balance is apparently 0.

Side note:

You're obviously using web3.js v0.x here; I think that web3.js v1.x would possibly throw an "invalid value for address type" exception on this, so it might be worth upgrading your web3.js version.