Helps IDE know how you will call your callback.

Sample

function callMeBack (callback) {
    Dexie.fakeAutoComplete(function() {
        callback ([new Date()]);
    });
}

Then, in your IDE, you write:

callMeBack (function (a) {
    a._  // Here the IDE will know that a is an array of Date objects and autoComplete array methods as you type
});

How it works

The function simply calls setTimeout(yourFunction) and then immediately calls clearTimeout(handle).

Performance implications

Doing a loop of 100,000 calls to fakeAutoComplete() will result in the same time consumption as setting a property to an object twice. It is extremely fast.