Expresso Project POST request callback question

In the Expresso project, and the X-Press Publishing project as well, I’m wondering why in the POST request callbacks, specifically in the callback, does an arrow function not work? The test only passes when using named function().

Just curious what the difference is between the two, particularly in this instance, that is causing the test to fail.


I’ve figured that it has something to do with being able to access the this.lastID property in the callback of the, but what the difference is exactly still escapes me…