How do we know if the token needs approval or not?

[rafaelfaria]

I am making an app that will sell the token after X seconds. However, I just want to make sure it approves once. I can't find a way to check if it has been approved or not unless I store this in my database.

Any tips?

[ricmoo]

You can use the ERC-20 allowance method to check the current allowance (see EIP-20).

Also, if you are issuing an approve followed by a transfer, as long as the bounces are sequential, you know the approve must occur earlier than the transfer.