How can a user of a dapp withdraw their ERC-20 tokens from L1 -> L2 using their web browser wallet?

[JayWelsh]

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Issue Description

Hi there, it seems to me that right now all documentation for performing a bridge from L2 -> L1 for an arbitrary ERC-20 token requires the use of a Node SDK. This is obviously an issue if anyone wants to make a withdrawal of their own tokens via a dapp frontend (i.e. signing the transaction/message via their web browser wallet such as Metamask).

How can I go about enabling dapp users to call proveWithdrawalTransaction & finalizeWithdrawalTransaction via their web browser?

In my setup, it wouldn't be an issue if I need to run some code on Node.js and then send some blob of data to be signed to the web frontend where the user can then sign the transaction/message and submit it to L1 using proveWithdrawalTransaction and/or finalizeWithdrawalTransaction. But it's an issue if the SDK requires the private key of the user who intends to sign the message/transaction since that user would be interfacing with Ethereum via their web browser and web wallet.

What do I do? As things stand I have L1 -> L2 bridging working, and I have the L2 -> L1 process working up to calling the withdraw function on L2, but I am stuck at the point of needing to enable the user to perform proveWithdrawalTransaction and finalizeWithdrawalTransaction via the web browser. I need to make it possible for the user to sign the tx in their browser without needing to input their private key into a Node.js execution environment. Again, I can run the Node.js SDK on the dapp's backend and provide a blob of data to the user to sign if that's a viable option, but how would I get this data which needs to be signed by the user on the frontend?

Any help is much appreciated.

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[opfocus]

Thinking that Optimism SDK requires a private key is a misunderstanding. In reality, it only needs a signer, and you can use Wagmi and ethers.js to obtain signature information. I'm not sure if I fully understand your question.

[JayWelsh]

Sorry, I don't know why but I made a silly mistake and thought that the JS SDK needed to run on Node. That's my bad, in case anyone makes the same mistake as me and finds this discussion, please be aware that you can run the SDK client-side ( https://sdk.optimism.io/ ).

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