How to check if a variable is set on chrome storage

Question

I have a little snippet working with LocalStorage but I cannot make it work on Chrome Storage scheme yet.

When my application starts I check a variable in localStorage

var bookNarration=parseInt(localStorage.getItem("narration"));

If that variable is undefined, it means that my app has been opened for the first time and I after handle bookLanguage in a switch using the "default" declaration.

switch(window.bookNarration) { case 2: window.narrationShift = window.spanishShift; break; case 3: window.narrationShift = window.frenchShift; break; case 10: window.narrationShift = window.neutralShift; break; default: window.narrationShift = 0; }

To make it work with Chrome Storage I change my code on this way:

var bookNarration=parseInt(chrome.storage.local.get("narration"));

But I immediately get this error:

Invocation of form get(string) doesn't match definition get(optional string or array or object keys, function callback)

I have been searching for many hours trying to find a solution but I can't make it work. I thing that I just need to check if the value is already defined so if It isn't, I could use set() method to store my default value.

James M · Accepted Answer · 2014-04-12 18:05:51Z

10

The function expects a callback:

chrome.storage.local.get("narration", function(data) { if(chrome.runtime.lastError) { /* error */ return; } var bookNarration = parseInt(data.narration); switch(bookNarration) { /* ... */ }; });

edited Apr 12, 2014 at 18:05

answered Feb 28, 2013 at 18:58

James M

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1 Comment

Gino Over a year ago

In my Chrome app, this chrome.runtime.lastError never work. i'm suprise that they didn't find a smartest way to manage error. It's easier with LocalStorage var students = JSON.parse(localStorage.getItem('studentsInfo') || [];

Troy Wray · Accepted Answer · 2017-11-06 07:58:12Z

There's no need to use the catch now (meaning I don't know if this changed since the accepted answer and now).

You can pass in the item(s) you want along with defaults should the item not exist

chrome.storage.local.get({narration: "", num: 0, books: []}, function(data) { var bookNarration = parseInt(data.narration); switch(bookNarration) { var numBooks= data.books.length /* ... */ }; });

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