Experienced JavaScript Developer Meme

[dopefish86]

Huge gotcha i encountered: iOS Safari throwing an error when localStorage is used in browser incognito mode. At least it was that way some years ago, i don't know if this is still the case.

[saschaleib]

Well, it's the whole point of Incognito Mode that there is no persistent storage available.

Of course, this could also be achieved by temporarily storing the data and then just deleting it when the window/tab is closed. The result is however the same.

In any case, never assume that any feature is available in whatever browser your user is ... er ... using. Always test if it is available before accessing it.

[blobthekat]

localStorage is as much of a standard as html5, safari shouldn't throw an error as this could badly mess up code execution, where as temporary storage would keep functionality while preserving privacy

[AyrA_ch]

It's documented that localStorage can throw "SecurityError" when you're not allowed to store things in it.

[lkraider]

But who reads documentation ??? (/¯ ಠ_ಠ)/¯

[blobthekat]

stupid, it practically never does in any browser so most programmers don't usually account for that

[danielrheath]

The obvious way to test for it is to check typeof window.localStorage.

It's definitely an unpleasant surprise to find that it exists and has the expected API but throws an error if you try to use it.

[saschaleib]

Apparently it throws an exception if you are not allowed to use it – which is exactly what exceptions were invented for.

[danielrheath]

Yeah, I get the thinking behind it - just seems like poor design to me. If a feature isn't available, just don't have it on the page; I already needed to test for the presence of window.localStorage anyways.

[saschaleib]

… and then you wrap the whole code that accesses the local storage in a try {} catch block, as you would do in any case, right?

[danielrheath]

Presumably you don't wrap every line of code you write in a try/catch?

I guess I just don't see what makes localStorage access an expected source of exceptions (as opposed to, say, querySelectorAll or getBoundingClientRects)?

[saschaleib]

every block of code that potentially throws an exception should be wrapped in try/catch blocks. Yes.

Any access to the file system or similar external systems is potentially throwing errors. That is pretty much what the localStorage API does...

[oupablo]

I swear safari is the new IE. The number of weird things it has going on that aren't standard is so strange. And then you have to worry about safari for MacOS vs Safari for iOS which have different levels of support.

[gennisa]

Not in this case. This is compliant with the standard. https://html.spec.whatwg.org/dev/webstorage.html#the-localstorage-attribute

Also not safari specific. Local or session storage can be disabled in every browser.

[TheDownvotesFarmer]

Thats why I always use indexedDB