1

I'm fairly new to programing and solidity, still on the learning curve of things here.... So right now I'm trying to check for the balance in Wei of the account I submit into the text field (Account). How do I achieve this functionality?

Check

My html code for this in index.html is;

<h1>Check</h1>
    <br><label for="acctAddress">Account:</label><input type="text" id="acctAddress" placeholder="e.g., 0x93e66d9baea28c17d9fc393b53e3fbdd76899dae"></input>
    <br><br><button id="check" onclick="checkBalance()">Check Balance</button>
    <br>
    <h3>You have <span class="green"><span id="acctBalance"></span> META</span>
    </h3>

The Metacoin Solidity in MetaCoin.sol function is;

function checkBalance(address _account) returns (uint balance) {
        return balances[_account];
    }   

The JavaScript function in app.js is

function checkBalance() {


    var acctAddress = document.getElementById("acctAddress").value;
    var check_element = document.getElementById("acctBalance");

    setStatus("Retreving Balance... (please wait)");

    web3.eth.getBalance(acctadd) 

      acctAddress = acctadd;


    }

};
1

I hope you are not mixing these 2 concepts:

  • The ether balance of your account, which you retrieve with web3.eth.getBalance(YOUR_ADDRESS).
  • The MetaCoin balance stored in the contract, which you retrieve with contractAddress.checkBalance(YOUR_ADDRESS).

So if your case, you want to:

function checkBalance() {
    var acctAddress = document.getElementById("acctAddress").value;
    var check_element = document.getElementById("acctBalance");

    setStatus("Retreving Balance... (please wait)");

    MetaCoin.deployed().checkBalance(acctAddress)
        .then(function(balance) {
            console.log(balance.toString(10));
            console.log(balance.toNumber());
        })
        .catch(function(error) {
            console.error(error);
        });
    }
};

Note that Truffle uses Ether-Pudding so your contract calls return promises.

| improve this answer | |
  • Thanks! I managed to get it to display the balance although it seems to be wrong, I sent 5 to the address 0xcb439bd73060413b5b24227bd2bad7b4263039b6, or could it be a conversion thing?!. I also managed to add a field that returns the transaction hash but i get an error. See screen shot here -> ![SS_meta.png](postimg.org/image/gb1w2wpwp) and The code functions here -> ![bal_tran.png](postimg.org/image/zfxaplm5f) – Kizito Oct 5 '16 at 17:29
  • Well, of course, you are using web3.eth.getBalance(). Read my answer again. – Xavier Leprêtre B9lab Oct 6 '16 at 8:47
1

Here is the way I'm doing it using Truffle and the Web3 API :

web3.eth.getBalance(address, 'latest', function(err, result) {
    if (err != null) {
        console.error("Error while retrieving the balance for address["+address+"]: "+err);
    }

    var balance = Number(web3.fromWei(result, "ether"));
    console.debug("Balance for address["+address+"]="+balance);
}); 

Please find below the full documentation :

web3.eth.getBalance

web3.eth.getBalance(addressHexString [, defaultBlock] [, callback]) Get the balance of an address at a given block.

Parameters

String - The address to get the balance of.

Number|String - (optional) If you pass this parameter it will not use the default block set with web3.eth.defaultBlock.

Function - (optional) If you pass a callback the HTTP request is made asynchronous. See this note for details.


EDIT: Full example

HTML

<label for="amount">Address:</label><input type="text" id="address" placeholder="0x***"></input>
<br><button id="send" onclick="checkBalance()">Check balance</button>
<label for="balance">Balance:</label><input type="text" id="balance" disabled></input>

Javascript

function checkBalance() {
    var address = document.getElementById("address").value;
    web3.eth.getBalance(address, 'latest', function(err, result) {
        if (err != null) {
            console.error("Error while retrieving the balance for address["+address+"]: "+err);
        }

        var balance = Number(web3.fromWei(result, "ether"));
        console.debug("Balance for address["+address+"]="+balance);

        var balance_element = document.getElementById("balance");
        balance_element.innerHTML = balance.valueOf();
    }); 
};
| improve this answer | |
  • Thanks @gjeanmart Could you please show me the corresponding html block and solidity block as well? – Kizito Oct 4 '16 at 22:02
  • Account, balance and transaction are native functions in Ethereum, You don't need a smart contract (in Solidity) to implement a GetBalance(add) function For the html code. I added a full example which should work – Greg Jeanmart Oct 4 '16 at 22:16
  • Thanks! I managed to get it to display the balance although it seems to be wrong, I sent 5 to the address 0xcb439bd73060413b5b24227bd2bad7b4263039b6, or could it be a conversion thing?!. I also managed to add a field that returns the transaction hash but i get an error. See screen shot here -> ![SS_meta.png](postimg.org/image/gb1w2wpwp) and The code functions here -> ![bal_tran.png](postimg.org/image/zfxaplm5f) – Kizito Oct 5 '16 at 17:28

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