Setting an array of objects to sessionStorage

Question

Ok, so I have this JSON:

{"Status":"OK!","ListaPermessi":
[{"IdPermesso":10,"Nome":"WIND_PARAMS"},
 {"IdPermesso":11,"Nome":"ADMIN_SERVER"},
 {"IdPermesso":21,"Nome":"REC"},
 {"IdPermesso":22,"Nome":"REC_DIST"},
 {"IdPermesso":23,"Nome":"REC_DIST_CR"}
]}

My code is:

var parsedResult = JSON.parse(result); // where result is the above JSON
if (parsedResult.Status === "OK!") {
    // Set sessionStorage vars
    if (typeof(Storage) !== "undefined") {
        // localStorage & sessionStorage support!

        sessionStorage.setItem("ListaPermessi", parsedResult.ListaPermessi);
    }
    else {
        // Sorry! No web storage support :(
    }
}

But... this is not working properly! After the assignment, the sessionStorage seen from Firebug looks like this:

sessionStorage:

• ListaPermessi = "[object Object],[object Object],[object Object],[object Object],[object Object]"

What is the proper way to assign an array of objects to a sessionStorage variable from javascript?

Unlace

Answer 1

You need to turn it back into a JSON string. You can do that with the JSON.stringify method:

sessionStorage.setItem("ListaPermessi", JSON.stringify(parsedResult.ListaPermessi));

The reason for this is that web storage can only store strings, and the default toString method of Object returns, as you've now seen, "[object Object]".

---

Side note: typeof is an operator, not a function, so there's no need for the parentheses:

if (typeof Storage !== "undefined") { //...

Quindecennial

Thanks for the quick answer! But, still not working! I've tried it and it parses the list as a string, not as an array of objects. – Unlace

@CosminT. - What do you mean? What is the result of JSON.stringify(parsedResult.ListaPermessi)? – Quindecennial

"[{"IdPermesso":10,"Nome":"WIND_PARAMS"}, {"IdPermesso":11,"Nome":"ADMIN_SERVER"}, {"IdPermesso":21,"Nome":"REC"}, {"IdPermesso":22,"Nome":"REC_DIST"}, {"IdPermesso":23,"Nome":"REC_DIST_CR"} ]". as a string, between "" – Unlace

@CosminT. - That's what you should get. You can only store strings in web storage. You can call JSON.parse on that value to convert it back into an actual JS data structure. – Quindecennial

That's the answer I was looking for! So it cannot have "an array structure". Thanks a lot! – Unlace

@CosminT. - You're welcome, glad I could help :) Just remember to always call JSON.stringify when storing, and JSON.parse when retrieving data to/from web storage. – Quindecennial