HTML and CSS Reference
In-Depth Information
Objective 1.4: Implement HTML5 APIs
JavaScript APIs have provided some new powerful functionality, such as the ability to store
more data locally and make that data available to the webpage through the Web Storage API.
The AppCache API allows you to take web applications offline. The Geolocation API provides
methods to work with global positioning within the application.
This objective covers how to:
Use the storage API
Use the AppCache API
Use the Geolocation API
Using the storage API
WebA Storage is a new API for storing webpage data locally. Web Storage, described in this
section, replaces the concept of cookies.
Of course, you must consider your audience's browser support for HTML5 and Web Storage
before you choose to use it exclusively.
Two forms of Web Storage exist: local and session storage. Local storage is persistent; data
stored in local storage is available to the webpage even if the user closes the browser com-
pletely and then reopens it to your site. Session storage is available only for the duration of
the current session, so if the user closes the browser, session storage is automatically cleaned
up and is no longer available. The Web Storage API is available as a global object. To access
local storage, use the localStorage object; to access session storage, use the sessionStorage
The localStorage and sessionStorage objects provide exactly the same API. All the examples
shown in this section work exactly the same with either object. The only difference is the
lifetime of the storage. Remember that sessionStorage is cleared when the session is closed,
whereas localStorage is still be accessible after a session closes and a new session opens.
Table 1-13 lists the API methods and their usage. Web Storage is implemented as name
value pairs and stored as strings. Any data that you can put into a string format can be stored
in Web Storage. This isn't as limiting as it sounds. You'll see some examples of storing complex
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