swapExactTokensForTokens not working!

Question

We are trying to "swapExactTokensforTokens" for swapping any token, and it runs well, but we get this error at the blockchain:

TRANSFER_FROM_FAILED

https://polygonscan.com/tx/0xf584e421990628131b92b22b2aad270e91752287817eeb518a4d9bdb4b37d086

When we use "swapETHForExactTokens" it makes the trade, but can only use MATIC/ETH/BNB as token1. Do you know how to solve this?

CODE (we are not approving contracts before, we don't know how to do it).

const tx = await router.swapExactTokensForTokens(
        amountIn,
        amountOutMin,
        [tokenIn, tokenOut],
        data.recipient,
        Date.now() + 1000 * 60 * 5, //5 minutes
        {
          'gasLimit': data.gasLimit,
          'gasPrice': data.gasPrice
      });

Thanks!

Answer 1

You need to approve, yes. In solidity, just is this:

IERC20(address(token)).approve(address(router), amountToApprove);

So, you just need to convert it to the language you are using, if you are not using solidity.

In ether.js, what I suppose you are using, check this:

Execute transaction Approve directly against contract address (without ABI)