[Ethereum] transfer ERC20 Tokens by web3

I suspect that your issue is because you have not approved the transfer required to call transferFrom(...).

Here are the relevant functions:

    /* Send coins */
    function transfer(address _to, uint256 _value) {
        if (balanceOf[msg.sender] < _value) throw;           // Check if the sender has enough
        if (balanceOf[_to] + _value < balanceOf[_to]) throw; // Check for overflows
        balanceOf[msg.sender] -= _value;                     // Subtract from the sender
        balanceOf[_to] += _value;                            // Add the same to the recipient
        Transfer(msg.sender, _to, _value);                   // Notify anyone listening that this transfer took place
    }

    /* Allow another contract to spend some tokens in your behalf */
    function approveAndCall(address _spender, uint256 _value, bytes _extraData)
        returns (bool success) {
        allowance[msg.sender][_spender] = _value;
        tokenRecipient spender = tokenRecipient(_spender);
        spender.receiveApproval(msg.sender, _value, this, _extraData);
        return true;
    }

    /* A contract attempts to get the coins */
    function transferFrom(address _from, address _to, uint256 _value) returns (bool success) {
        if (balanceOf[_from] < _value) throw;                 // Check if the sender has enough
        if (balanceOf[_to] + _value < balanceOf[_to]) throw;  // Check for overflows
        if (_value > allowance[_from][msg.sender]) throw;   // Check allowance
        balanceOf[_from] -= _value;                          // Subtract from the sender
        balanceOf[_to] += _value;                            // Add the same to the recipient
        allowance[_from][msg.sender] -= _value;
        Transfer(_from, _to, _value);
        return true;
    }

If you are the current owner of the tokens, you can call transfer(...) to transfer your balance to another address.

However if you want to transfer from another address, you will need to call transferFrom(...) which will check the allowance[...][...] data structure to confirm whether this transfer has been approved.

So, call approveAndCall(...) first to approve your transfer and you should be able to call transferFrom(...) to transfer your tokens.

When you call transferFrom(...) without first calling approveAndCall(...), and error is thrown in the line

if (_value > allowance[_from][msg.sender]) throw;   // Check allowance

This error will appear as an Out Of Gas error in the Ethereum Wallet.

If you are comfortable using geth, see How can the transaction status from a thrown error be detected when gas can be exactly the same as the gasUsed for a successful transaction? for the following code that can be used to check the exact reason for your error:

> var status = debug.traceTransaction("0xd23219e2ea10528b245deb9e47993cae2ffd3ffe9fc27aeb808e94fc4e75d37b")
undefined
> if (status.structLogs.length > 0) {
  console.log(status.structLogs[status.structLogs.length-1].error)
}
"invalid jump destination (PUSH1) 2"

If you are using Ethereum wallet, the cleaner way is to `Watch Token

• Go to contracts Tab.
• Click on Watch Token
• Enter details like Token Contract Address, Token Name, Token Symbol, Decimal Places of smallest unit
• Click Ok

And you will be able to see balances.

To execute functions of the contract like 'transfer, you need to Watch Contract.

• Go to contracts Tab.
• Click on Watch Token
• Enter details like Contract Name, Contract Address, JSON Interface (Contract ABI)
• Click Ok
• Now the contract will be listed under contracts tab and you can call any of it's functions

If you are not using Ethereum wallet and want to continue using geth, probably you should write functions for the actions like checkBalance, transferCoin using web3.js.