I consider Javascript more modern

A lot of people don’t want to have to write Lua, to eg handle clicks on buttons. And how would you embed Lua scripts safely on the web, anyway?

You don't have to write Lua. As you've already said in a different comment, it isn't a problem in QuickJS because it has memory limiting built in. IMO that's the right way to do this - instead of transpiling JS to try and make it safe you should run it in a virtual machine like QuickJS/Lua/etc does.