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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 |
Browser compatibility
| 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.