Storage.key()

The key() method of the Storage interface, when passed a number n, returns the name of the nth key in the storage. The order of keys is user-agent defined, so you should not rely on it.

Syntax

var aKeyName = storage.key(key);

Parameters

key: An integer representing the number of the key you want to get the name of. This is a zero-based index.

Returns

A DOMString containing the name of the key.

Example

The following function iterates over the local storage keys:

function forEachKey(callback) {
  for (var i = 0; i < localStorage.length; i++) {
    callback(localStorage.key(i));
  }
}

Note: For a real world example, see our Web Storage Demo.

Specifications

Specification	Status	Comment
Web Storage (Second edition) The definition of 'key()' in that specification.	Recommendation

Feature	Chrome	Firefox (Gecko)	Internet Explorer	Opera	Safari (WebKit)
localStorage	4	3.5	8	10.50	4
sessionStorage	5	2	8	10.50	4

Feature	Android	Firefox Mobile (Gecko)	IE Phone	Opera Mobile	Safari Mobile
Basic support	2.1	?	8	11	iOS 3.2

All browsers have varying capacity levels for both localStorage and sessionStorage. Here is a detailed rundown of all the storage capacities for various browsers.

Note: since iOS 5.1, Safari Mobile stores localStorage data in the cache folder, which is subject to occasional clean up, at the behest of the OS, typically if space is short.