Date.gettime() is not a function, undefined - ios

Question

It is working on android and browser and WAS working on iOS (ionic view and device). I am saving a date inside my local Storage (import { Storage } from '#ionic/storage';) then compare it to a another date
Here's what I do And is working everywhere but suddenly, not ios under ionic view. Last test was maximum 2 weeks ago and was working as intended !
this.storage.get(filename).then((metadata_stored) => {
if (metadata_stored && metadata_stored.date && metadata_stored.date.getTime() === filedate.getTime())
//do something
and I get TypeError: metadata_stored.date.getTime() is not a function; metadata_stored.date.getTime is undefined.
filedate is create through something like this filedate: Date = new date("2017-10-14T15:44:48+02:00") (supposedly an ISO). Then it is saved in my local storage : this.storage.set(filename, { /* ... */ , date: filedate })
If I display metadata_stored.data, I get something like 2017-08-13T13:44:10.000Z
I don't get why it suddenly and silently stopped working. And how to correct it since metadate.date is an old value of filedate and filedate is a new Date(...) ! No code were changed in this section last 2 weeks.
Edit: I solved it by doing (new Date(metadata_stored.date)).getTime() instead. But I still have no idea why it stopped working for no reason...

Answer 1

In local storage, everything is stored as a string.
That means you should use (new Date(metadata_stored.date)).getTime() because metadata_stored.date is a string, not a Date.
let a = new Date();
let b = new Date();
// 2017-11-30T18:01:01457Z object
console.log(a, typeof a);
// 2017-11-30T18:01:01457Z object
console.log(b, typeof b);
localStorage.a = a;
localStorage.b = b;
a = localStorage.a;
b = localStorage.b;
// Thu Nov 30 18:01:01 GMT+0000 (GMT Standard Time) string
console.log(a, typeof a);
// Thu Nov 30 18:01:01 GMT+0000 (GMT Standard Time) string
console.log(b, typeof b);
a = new Date(localStorage.b);
b = new Date(localStorage.a);
// 2017-11-30T18:01:01457Z object
console.log(a, typeof a);
// 2017-11-30T18:01:01457Z object
console.log(b, typeof b);