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?

James Allardice · Accepted Answer · 2012-09-24 10:06:36Z

32

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") { //...

answered Sep 24, 2012 at 10:06

James Allardice

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6 Comments

Teslo. Over a year ago

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.

James Allardice Over a year ago

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

James Allardice Over a year ago

@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.

Teslo. Over a year ago

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

James Allardice Over a year ago

@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.

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