local storage
TRANSCRIPT
HTML 5 API: Documentation
http://www.whatwg.org/specs/web-apps/current-work/multipage/
http://dev.w3.org/html5/
localStorage, sessionStorage
AND YOU!
DOM Storage:
DOM Storage: Why?
Minimize HTTP Requests by not submitting unnecessary requests or statefullness
Store data in browser across tabs, windows, and sessions
Maintain functionality with unreliable connection by queuing data on reconnect Great for mobile web apps
Save user preferences Save session statefulness
DOM Storage: Browser Support
Firefox 3.5, Safari 4, IE8, Chrome 4+, Opera 10.5: HTML5 localStorage; these modern browsers all support the core localStorage functionality defined in the HTML5 draft.
DOM Storage: Browser Support(cont’d)
Firefox 2.x and 3.0: Gecko globalStorage, a very early implementation similar to HTML5’s localStorage.
Safari 3.1 & 3.2: HTML5 Database Storage, because Safari 3.1 and 3.2 don’t support HTML5 localStorage.
DOM Storage: Browser Support(cont’d)
IE6, IE7: userData persistence, a rarely used IE feature for associating string data with an element on a web page and persisting it between pageviews.
Google Chrome Pre 4: Gears Database API, pre-installed into into earlier versions of Chrome
Storage Objects
“Each domain and subdomain has its own separate local storage area. Domains can access the storage areas of subdomains, and subdomains can access the storage areas of parent domains.”- http://msdn.microsoft.com/en-us/library/cc197062(VS.85).aspx
Important For this origin check, HTTP and HTTPS are considered the same protocol.
Storage Objects (cont’d)
Domains: localStorage['example.com'] is accessible
to example.com localStorage[‘example.com’] is accessible to
www.example.com
Subdomains: localStorage['www.example.com'] is accessible
to example.com localStorage['www.example.com'] is NOT
accessible to mail.example.com
Storage Objects (cont’d)
Properties stored as Strings Numbers, Booleans, and Objects must be converted
If property name DNE, a key/value pair is automatically created to hold it
It appears that all browsers delete local storage objects by deleting cookies
IE is limited to only 5MB for localStorage and 5MB for sessionStorage
"The current default on iPhone is 5.0 MB. If your database grows beyond this limit, the user will automatically be asked to allow or deny the size increase. If he allows the increase, the database size limit will be upped to 10.MB“- http://building-iphone-apps.labs.oreilly.com/ch05.html#ch05%5Fid35933104
localStorage
“The local storage mechanism spans multiple windows and persists beyond the current session. ThelocalStorage attribute provides persistent storage areas for domains. It allows Web applications to store nearly 10 MB of user data, such as entire documents or a user's mailbox, on the client for performance reasons.”- http://msdn.microsoft.com/en-us/library/cc197062(VS.85).aspx
sessionStorage
“Session storage is designed for scenarios where the user is carrying out a single transaction. ThesessionStorage attribute of the window object maintains key/value pairs for all pages loaded during the lifetime of a single tab (for the duration of the top-level browsing context). For example, a page might have a check box that the user selects to indicate that he wants insurance.”- http://msdn.microsoft.com/en-us/library/cc197062(VS.85).aspx
DOM Storage: API
Storage ObjectlocalStorage and sessionStorage are both instances of the Storage object
Methods clear getItem removeItem setItem Key
Properties constructor length remainingSpace (IE Only)
DOM Storage: API Methods getItem: Retrieves the current value associated with the key.
value = window.localStorage.getItem(key);
setItem: Sets a key/value pair. window.localStorage.setItem(key, value);
removeItem: Deletes a key/value pair from the DOM Storage collection. window.localStorage.removeItem(key);
clear : Removes all key/value pairs from the DOM Storage area. window.localStorage.clear();
key: Retrieves the key at the specified index in the collection. keyValue = window.localStorage.key(n);
DOM Storage: API Properties constructor: Returns a reference to the
constructor In FF, localStorage.constructor !==
Storage ??
length: Retrieves the length of the key/value list.
remainingSpace (IE Only): Retrieves the remaining memory space, in bytes, for the storage object.
DOM Storage: API Properties (cont’d)
Getter/setters: key values can be used as properties of localStorage in place of getItem or setItem localStorage.x = ‘hey’▪ // localStorage.getItem(‘x’) === ‘hey’
localStorage.setItem(‘x’,’you’);▪ // localStorage.x === ‘you’
Examples
http://sammystodos.brandonaaron.net/#/list/0
sadf
Client-side SQL:
Currently only in Webkit & WebOS Chrome 3+ (3,4 via Gears), Safari 3.1+,
iPhone, Palm, Android http://
dev.w3.org/html5/webdatabase/ “The client-side SQL database in
HTML 5 enables structured data storage.”
SQL API: Database Object
MethodsopenDatabase transaction readTransactionchangeVersion: Change the DB’s
version.
Propertiesversion: The DB’s current version.
SQL API: openDatabase
window.openDatabase( DatabaseName, DatabaseVersion, DisplayName, EstimatedSize ) DatabaseName: non-empty String DatabaseVersion: If not the most recent version,
openDatabase will fail. DisplayName: any valid String (can be empty) EstimatedSize: an estimated size in bytes
var db = openDatabase(“DallasJS", “1.0",
“DallasJS’ sweet DB", 1024*1024);
SQL API:transaction & readTransaction
db.transaction(transactionCallback, errorCallback) db.transaction(function(tx) {
// EXECUTE SQL CODE VIA tx HERE}, function(e) {
alert(tx,e);});
The SQLTransaction Object has only method: executeSql
SQL API: executeSql
transaction.executeSQL( SQLStatement, SQLParameters, ResultsetCallback, ErrorCallback ); SQLStatement: A valid SQLite statement SQLParameters: Array of values▪ “Replace each ? placeholder with the value of the
argument in the arguments array with the same position.“
ResultsetCallback: Method to handle the returned results
ErrorCallback: Method to handle a failed execution
SQL API: executeSql (cont’d)
db.transaction(function(tx) {tx.executeSql(
"SELECT * FROM MyTb WHERE id = ?”,[1],function(tx, SQLResultSet ) {
console.log(result.rows.item(0)['id']);
});
});
SQL API: SQLResultSet
Properties insertId: The id of the of the inserted
row. rowsAffected: Number of rows
affected by the statement. rows: The resulting data list.
SQL: Examples
http://webkit.org/demos/sticky-notes/index.html
db.transaction(function(tx) {tx.executeSql("CREATE TABLE t1 (t1key INTEGER PRIMARY KEY,data TEXT,num double,timeEnter DATE); INSERT INTO 't1' VALUES(1, 'This is sample data', 3, NULL); INSERT INTO 't1' VALUES(2, 'More sample data', 6, NULL); INSERT INTO 't1' VALUES(3, 'And a little more', 9, NULL);");});
Cache Manifest
“The mechanism for ensuring Web applications are available even when the user is not connected to their network is the manifest attribute on the html element.”
1. Build WebApp in the form of HTML, CSS, JS, IMG files, etc…
You don’t need to include the current HTML file2. Add link to manifest in html
<html manifest=“example.manifest”>3. Make manifest file with MIME type “text/cache-
manifest” with paths to resources to be cached:
Cache Manifest: ExampleCACHE MANIFEST# versionNumber
CACHEexample.htmlexample.cssexample.jsexample.png
FALLBACK: * /sorry-i-am-offline.html#give 404 page for all non-cached items when offline
NETWORK: /important.html # never cache
Cache Manifest: Events
checking: Fired whenever a manifest is present, regardless if page has been visited.
downloading: If this cache manifest has never been seen before. progress: Fired during downloading phase giving updates
regarding progress. cached: Fired on completion. WebApp is now fully cached
noupdate: Fired if cache manifest has been seen, but is not new. downloading & progress: See above. updateready: New manifest has been cached, but your current
app is not utilizing it yet. error: 404, 410, Failed to download manifest or a resource obsolete: The manifest was found to have become a 404
or 410 page, so the application cache is being deleted.
Cache Manifest:applicationCache Object
The application cache automatically updates only if the manifest file changes. It does not automatically update if resources listed in the manifest file change
applicationCache.status: 0-5, corresponds with the following: UNCACHED // === 0 IDLE // === 1 CHECKING // === 2 DOWNLOADING // === 3 UPDATEREADY // === 4 OBSOLETE // === 5
applicationCache.update() applicationCache.swapCache()
Cache Manifest: iPhone EX
http://www.technetra.com/2009/08/17/countdown-html5-cache-version/
Are we Offline?
“The navigator.onLine attribute must return false if the user agent will not contact the network when the user follows links or when a script requests a remote page (or knows that such an attempt would fail)...”- http://www.whatwg.org/specs/web-apps/current-work/#offline
navigator.onLine === true window.addEventListener('online',function()
{console.log(‘We’re online!');},true); window.addEventListener(‘offline',function()
{console.log(‘We’ve lost power!');},true);
Additional Citations
http://html5demos.com/drag http://www.w3.org/TR/webstorage/ http://dev.w3.org/html5/ https://
developer.mozilla.org/en/dom/storage
http://www.sqlite.org/docs.html http://
www.w3.org/TR/2008/WD-html5-20080610/structured.html