sessionStorage isn't working as expected

Question

Here is my code:

    sessionStorage.loggedIn = true;

    if (sessionStorage.loggedIn) {
        alert('true');
    }
    else {
        alert('false');
    }

Simple enough. There must be some small thing I'm not understanding about how JavaScript is evaluating these expressions. When I put sessionStorage.loggedIn = false, the "false" alert shows correctly. However, when I change sessionStorage.loggedIn to true, the "false" alert still pops, even after clearing the session. What am I not getting right with this expression? It seems so simple, maybe I just need another pair of eyes on it.

Your code does exactly what you expect it to do in Firefox. What browser are you using? *edit* Chrome works too. — Pointy, Aug 19 '13 at 17:40
For reasons I'm not entirely sure of when I assign true to sessionStorage.loggedIn it becomes a string. This may be the problem you're having. — Doug Morrow, Aug 19 '13 at 17:45
Possible duplicate of [Cannot set boolean values in LocalStorage?](http://stackoverflow.com/questions/3263161/cannot-set-boolean-values-in-localstorage) — T.Todua, Aug 24 '16 at 15:59

Martin Jespersen · Accepted Answer · 2013-08-19T21:28:31.350

Try to change your code to

sessionStorage.setItem('loggedIn',JSON.stringify(true));

if (JSON.parse(sessionStorage.getItem('loggedIn'))) {
    alert('true');
}
else {
    alert('false');
}

and it should work consistently across all major browsers.

The interface with the setItem/getItem methods is how the spec is written, so going that way is safer than using the shortcut of assigning properties. Also, sessionStorage, like localStorage is a textbased storage mechanism, and not meant for storing objects, so you need to wrap calls with JSON.parse and JSON.stringify to get the expected results across the board.

Be aware that JSON.parse doesn't always play nice with undefined/null values, so it might be wise to do some type checking first.

You can read the spec for the storage interface here

Thanks for this, I love when answering a question teaches you best practice too! — Doug Morrow, Aug 19 '13 at 17:53
Thanks! I know there was some weird browser-related thing I wasn't finding by Googling. — Paul Erdos, Aug 20 '13 at 13:42

score 1 · Answer 2 · answered Aug 19 '13 at 17:49

Keys and Values in a WebStorage object (sessionStorage) must be strings. If they are not strings they "should" be converted to strings in the browser's implementation when you assign to sessionStorage. If you evaluate against "true" or convert to boolean it will work fine.

https://code.google.com/p/sessionstorage/

http://www.w3schools.com/html/html5_webstorage.asp

sessionStorage isn't working as expected

2 Answers2

Linked