JavaScript authoritative guide Section 20 client memory

Client memory

Several forms of client storage:

Web Memory

Cookies

IE UserData

Offline applications

Web Database

File System API

20.1 Localstorage and Sessionstorage

20.1.1 Storage expiration and scope

The difference between Localstorage and Sessionstorage is that the storage has a different validity period and scope.

The scope of the Localstorage is limited at the document source level.

Document Source: protocol hostname port determines the same document source

Source documents can share the same localstorage, and can even change and overwrite localstorage.

The scope of Localstorage is limited by different browser vendors.

Source documents can share the same sessionstorage, the scope is limited to the form, and the form here refers to the top-level form.

<iframe> of homologous document sources can share sessionstorage.

Test whether the browser supports this feature:

<strong>function Test () {var a = Window.localstorage;if (a) {alert ("Your browser supports Localstorage");} else {Ale RT ("Your browser Dosen ' t support Localstorage");}} </strong>

20.1.2 Storage API

Manipulating storage objects and properties

<strong>localstorage.setitem ("UserName", "Michael"); Localstorage.getitem (); Localstorage.removeitem (); Localstorage.delete (); Localstorage.clear ();</strong>

20.1.3 Storage Events

local storage for HTML5. A storage event is also provided . Ability to listen for changes to key-value pairs, such as the following:

if (Window.addeventlistener) {
Window.addeventlistener ("Storage", handle_storage,false);
}else if (window.attachevent) {
Window.attachevent ("Onstorage", handle_storage);
}
function Handle_storage (e) {
if (!e) {e=window.event;}
Showstorage ();
}

20.2 Cookies

20.2.1 Cookie Expiration and scope

Not to be continued

Copyright notice: This article blog original articles, blogs, without consent, may not be reproduced.

JavaScript authoritative guide Section 20 client memory