Approve BUSD token in pancakeswap

Question

im new in blockchain and i´m playing with the web3 javascript library. I´m trying to approve the BUSD token to do a swap. My js code is something like this:

async function approveToken(web3, c, howMuchTokentoApprove, senderAddress) {
    var abi = [ {
        "constant": false,
        "inputs": [
          { "internalType": "address", "name": "spender", "type": "address" },
          { "internalType": "uint256", "name": "amount", "type": "uint256" },
        ],
        "name": "approve",
        "outputs": [{ "internalType": "bool", "name": "", "type": "bool" }],
        "payable": false,
        "stateMutability": "nonpayable",
        "type": "function",
      },];
    try {
        var contract = new web3.eth.Contract(abi, c);

        var nonceResponse = await web3.eth.getTransactionCount(senderAddress); 
        var nonce = nonceResponse;
        var txParams = {
            gas: web3.utils.toHex(gasLimit),
            gasPrice: web3.utils.toHex(gasPrice),
            nonce: web3.utils.toHex(nonce),
            chainId: chainId,
            to: c
        };

        
        txParams.data = await contract.methods.approve(senderAddress,
                                howMuchTokentoApprove).encodeABI();

        var signedTx = await web3.eth.accounts.signTransaction(txParams, process.env.senderPrivateKey);
        nonce += 1;
        txParams.nonce = web3.utils.toHex(nonce);
        await web3.eth.sendSignedTransaction(signedTx.rawTransaction);
        console.log("Token spending approved. \n");
        txAlreadyApprove = true;
        return true
    } catch (error) {
        console.log('err', error);

    }
} 

• c variable is this address (the busd token in bsc) https://bscscan.com/token/0xe9e7cea3dedca5984780bafc599bd69add087d56

• senderAdddres is the wallet that wants to do the swap (my wallet)

But when i execute the code, the this is the result: https://bscscan.com/tx/0xd542a08538d39e54603b6aa40d6914f7240ba67519b4a9eebd8261f5d2eaf51e

The log show my wallet:

Approved BUSDFor Trade On0xb78314255250be3f4cfcba6205d1c1d02b06aba5

But, if i execute the operation with the pancake UI. This is the result: https://bscscan.com/tx/0x80a3008132ddcc8af290e9a62fbb8b21b8b33118d3da60a0392bae7d44847950

Approved BUSD For Trade OnPancakeSwap: Router v2

What i´m doing wrong?

Thank you! and happy new year!!

Answer 1

The difference is that in the first transaction you are approving yourself

MethodID: 0x095ea7b3
[0]:  000000000000000000000000b78314255250be3f4cfcba6205d1c1d02b06aba5
[1]:  0000000000000000000000000000000000000000000000003782dace9d900000

And the Pancake UI is approving the Pancake Router contract https://bscscan.com/address/0x10ed43c718714eb63d5aa57b78b54704e256024e#code

MethodID: 0x095ea7b3
[0]:  00000000000000000000000010ed43c718714eb63d5aa57b78b54704e256024e
[1]:  ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff

The value ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff is used for some tokens to indicate infinite approval.