Until now, the work on the HTTP POST for uploading a file to S3 has focused on the form creation and submit interception. With this episode, the work makes a shift from the front-end in the browser, to the back-end in the Node / Express server that has been created.
The API is already handling the request for the needed form data, so it's time to generate the actual S3 upload policy with cryptographic signature.
In this episode, you'll see 2 libraries that are used to handle this feature.
With these two libraries installed via npm, the process of creating the policy and returning it through the API call is fairly straightforward.