I am getting reason: 'invalid BigNumber value', Error. What is the reason?

Question

wallet = ethers.Wallet.fromMnemonic(mnemonic)
// console.log(wallet.address)
const signer = wallet.connect(provider);
// console.log(signer)

const routerInstance = new ethers.Contract(routerAddress, routerABI, signer);
const token1 = new ethers.Contract(fromAddress, erc20ABI, provider);
const token2 = new ethers.Contract(toAddress, erc20ABI, provider);





//--------------------------Input variabals--------------------------//




const gasLimit = 20000




//--------------------------Token Swap Function--------------------------//




const TokenSwap = async(amount, fromAddress, toAddress) => {

    const decimal1 = await token1.decimals()
    const decimal2 = await token2.decimals()

    // const amountIn = ethers.utils.parseUnits(amount, decimal1).toString();
    // const amountIn = ethers.BigNumber.from(amount, decimal1).toString();
    const amountIn = ethers.utils.parseEther(amount).toString();
    const amountOut = await routerInstance.getAmountsOut(amountIn, [fromAddress, toAddress])
    console.log(amountIn)

    const output = ethers.utils.formatUnits(amountOut[1].toString(), decimal2)
    console.log(output)
    console.log(Date.now() + 1000 * 60 * 10)
    const tx = await routerInstance.swapTokensForExactTokens(
        amountIn,
        amountOut,
        [fromAddress, toAddress],
        wallet.address,
        Date.now() + 1000 * 60 * 5,
    )
}

amount = "0.000000000000002";
TokenSwap(amount, fromAddress, toAddress);


                ^

Here is my error:

D:\blockchain\Volume Bot -ruv\node_modules\@ethersproject\logger\lib\index.js:238
        var error = new Error(message);
    Error: invalid BigNumber value (argument="value", value=[{"type":"BigNumber","hex":"0x07d0"},{"type":"BigNumber","hex":"0x00"}], code=INVALID_ARGUMENT, version=bignumber/5.7.0)
        at Logger.makeError (D:\blockchain\Volume Bot -ruv\node_modules\@ethersproject\logger\lib\index.js:238:21)
        at Logger.throwError (D:\blockchain\Volume Bot -ruv\node_modules\@ethersproject\logger\lib\index.js:247:20)
        at Logger.throwArgumentError (D:\blockchain\Volume Bot -ruv\node_modules\@ethersproject\logger\lib\index.js:250:21)
        at BigNumber.from (D:\blockchain\Volume Bot -ruv\node_modules\@ethersproject\bignumber\lib\bignumber.js:239:23)
        at NumberCoder.encode (D:\blockchain\Volume Bot -ruv\node_modules\@ethersproject\abi\lib\coders\number.js:36:39)
        at D:\blockchain\Volume Bot -ruv\node_modules\@ethersproject\abi\lib\coders\array.js:74:19
        at Array.forEach (<anonymous>)
        at pack (D:\blockchain\Volume Bot -ruv\node_modules\@ethersproject\abi\lib\coders\array.js:60:12)
        at TupleCoder.encode (D:\blockchain\Volume Bot -ruv\node_modules\@ethersproject\abi\lib\coders\tuple.js:71:33)
        at AbiCoder.encode (D:\blockchain\Volume Bot -ruv\node_modules\@ethersproject\abi\lib\abi-coder.js:91:15) {   reason: 'invalid BigNumber value',   code: 'INVALID_ARGUMENT',   argument: 'value',   value: [
        BigNumber { _hex: '0x07d0', _isBigNumber: true },
        BigNumber { _hex: '0x00', _isBigNumber: true }   ] }
    
    Node.js v20.9.0

Answer 1

Decoding your error shows that 0x07d0 corresponds to decimal 2000.

And 0x00 corresponds to decimal 0.

Which means that the problem is with one of your amountIn or amountOut parameters.

Considering amountIn is converted to string on this line (const amountIn = ethers.utils.parseEther(amount).toString();), you should look into how you're pass amountOut in:

const amountOut = await routerInstance.getAmountsOut(amountIn, [fromAddress, toAddress])

amountOut is actually an array here, you can look that up in the UniswapRouter02.sol ABI, or the function here:

function getAmountsOut(uint amountIn, address[] memory path) public view returns (uint[] memory amounts);

So in your ethers.js project you should pick a specific slot from the return value and then convert it to string, because all BigNumber values should be converted to string before used in ethers.js contracts.

Like this:

const tx = await routerInstance.swapTokensForExactTokens(
        amountIn,
        amountOut[0].toString(),
        [fromAddress, toAddress],
        wallet.address,
        Date.now() + 1000 * 60 * 5,
    );