github: comment will be remaining even if reload browser, why?

Question

When I write a comment with github's issue page, I noticed that the comment body remains even if I reload the browser.

I have checked localStorage, sessionStorage, cacheStorage, IndexedDB, cookie, but I found no instance of the sentence that I wrote.

Also, I have checked the network tab of Chrome Devtool, but I could not find any suspicious network traffic.

How does github.com achieve this recovery function?

Answer 1

They are using SessionStorage to do this:

On Page Leave:

1. select all of the input fields with .js-session-resumable as selector
2. put {id, value} pair of inputs in an array
3. put it in SessionStorage as session-resume:/current/page/path

On Page Load:

1. check if there are any values with session-resume:/current/page/path key in SessionStorage
2. if yes, update values of inputs and remove this record from SessionStorage

Note: If you write a comment in a page (without submitting it) and go to another page, then you can see your comment saved in SessionStorage.