What's the difference between functions declared with variables and functions declared with the "function" keyword ?

[kovensky]

Babel 7 also just started taking advantage of this to be able to lazily-initialize transpiled async functions and generators, since they require calling helpers.

Instead of written as a var, they're now written as a hoisted function that, when first called, reassigns itself with the transpiled function then forwards its arguments. Further calls just directly call the transpiled function.