reading-notes

Local Storage

Persistant local Storage

• advantage over native client applications
• OS has abstract layer for storing and retrieving application specific data
• stored in registry, INI files, XML files or other platform convention
• can embed your own database, invent your own file format, etc.

Cookies

• invented early in web history
• can be used for persistent local storage
• included in every HTTP request
• slows down data
• sends data unencrypted over internet
• limited to 4kb data

Internet Explorer

• Microsoft is tricksy, make us believe it was the only….
• invented DTHML Behaviors
  • userData
    • allows web page to store up to 64 kb data
    • heirarchical XML based structure

Flash

• created in 2002
• Adobe introduced Flash 6, misleading name of “Flash Cookies”
• Local Shared Objects store up to 100 kb of data

Gears

• 2007 by Google
• geolocation API in IE

HTML 5 Storage

• Web Storage
• Web pages store named key/value pairs locally
• Data never transmitted

Check for storage

function supports_htrml5_storage() {
  try {
    return 'localStorage' in window && window['localStorage'] ~== null;
  } catch (e) {
    return false;
  }
}

• Modernizr

if (Modernizr.localstorage) {
} else {
}

Using HTML 5 Storage

interface Storage {
  getter any getItem(in DOMString key);
  setter creator void setItem(in DOMString key, in any data);
};

var foo = localStorage.getItem("bar");
// ...
localStorage.setItem("bar", foo);

``` var foo = localStorage[“bar”]; // … localStorage[“bar”] = foo;

interface Storage { deleter void removeItem(in DOMString key); void clear(); };

interface Storage { readonly attribute unsigned long length; getter DOMString key(in unsigned long index); };

### Tracking changes

``` if (window.addEventListener) {
  window.addEventListener("storage", handle_storage, false);
} else {
  window.attachEvent("onstorage", handle_storage);
};

function handle_storage(e) {
  if (!e) {e = window.event; }
}

Limitations in current browsers

• 5 mg storage space each origin gets by default

Beyond

• Indeed Database API or “WebSimpleDB” or IndexedDB
  • exposed object store
  • object store shares concepts with SQL

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