- For native applications, the operating system typically provides an abstraction layer for storing and retrieving application-specific data like preferences or runtime state. These values may be stored in the registry, INI files, XML files, or some other place according to platform convention.
- Cookies are included with every HTTP request, thereby slowing down your web application by needlessly transmitting the same data over and over
- Cookies are included with every HTTP request, thereby sending data unencrypted over the internet (unless your entire web application is served over SSL)
- Cookies are limited to about 4 KB of data — enough to slow down your application (see above), but not enough to be terribly useful
- HTML5 Storage is a way for web pages to store named key/value pairs locally, within the client web browser. Like cookies, this data persists even after you navigate away from the web site, close your browser tab, exit your browser, or what have you. Unlike cookies, this data is never transmitted to the remote web server
- The data can be any type supported by JavaScript, including strings, Booleans, integers, or floats. However, the data is actually stored as a string. If you are storing and retrieving anything other than strings, you will need to use functions like
parseInt() or parseFloat() to coerce your retrieved data into the expected JavaScript datatype.
- Calling
setItem() with a named key that already exists will silently overwrite the previous value. Calling getItem() with a non-existent key will return null rather than throw an exception.
- Like other JavaScript objects, you can treat the localStorage object as an associative array. Instead of using the
getItem() and setItem() methods, you can simply use square brackets.
- If you want to keep track programmatically of when the storage area changes, you can trap the
storage event. The storage event is fired on the window object whenever setItem(), removeItem(), or clear() is called and actually changes something.