Optimization: avoid checking null proto twice

[matthieusieben]

When the loop is run for the first time, we already know that the protoype is not null (because of the if before). We can thus make one fewer evaluation of Object.getPrototypeOf(proto) !== null by performing a do while loop

[jsf-clabot]

All committers have signed the CLA.

[aminya]

Yes with the preceding check this is true:

  if (Object.getPrototypeOf(value) === null) {
    return true
  }
  let proto = value