Why do associative arrays don't work in localStorage[""]?

Question

For example I have the following code:

  localStorage["screenshots"] = new Array();
  localStorage["screenshots"]["a"] = 9;
  alert(localStorage["screenshots"]["a"]);

  Arr = new Array();
  Arr["screenshots"] = new Array();
  Arr["screenshots"]["a"] = 9;
  alert(Arr["screenshots"]["a"]);

(I use Google Chrome v9.0.597.107 on Windows Vista 32-bit)

But only the second part works (output of alert() is "a")! The first alert outputs in contrast "undefined"!

What is the problem?

Thanks.

Answer 1

localStorage stores values as strings, so you need to JSON serialize your objects on the way in and deserialize them on the way out. For example:

var data = {'A': 9};

localStorage['screenshots'] = JSON.stringify(data);

// Later/elsewhere:

var data = JSON.parse(localStorage['screenshots']);

// 9
console.log(data.A);