In the current demo, every time the code in the left panel is changed,
the new code is stored in the URL hash, which pushes a new history
entry. This effectively "breaks" the back button. This change calls
`history.replaceState` instead, so a single click of the back button
will return the browser to whatever page was open before navigating to
the demo.

We inline function definitions but we shouldn't inline new expressions,

835befe introduced both call expressions and new expressions. Call expressions have been removed but looks like new haven't.

This is a common pattern to write default values.

I've started the discussion around it but I think that it was a mistake. It feels weird to add parenthesis on object values sometimes but not others. I think that it's best to let prettier do its work on staying under 80 columns based on the rules we added.

Added a link to Mads Kristensen's new VS extension for prettier

…714)

This has come up many times in the past and while going through the fb codebase, there are a few instances where we group array elements logically using empty lines and it's a shame that they are gone.

Fixes #703

We already do it for if/... but it looks weird for arrow function body.

There is an off by one error which made the algorithm not work all the time. In many cases, it actually is the opposite, so whenever you save, it adds/removes that line. I noticed it during the --debug-check run on our codebase but didn't investigate.

Fixes #723