Storage : Object

Storage allows saving data in the web browser
that can be retrieved in future views of the web page.

The browser has two types of storage:
%%/Window#localStorage|**localStorage**%% which stores
data across page views, browser restarts and computer restarts,
and 

%%/Window#sessionStorage|**sessionStorage**%% which only stores
data across page views. **sessionStorage** is deleted when the
user closes the browser.

----
instance[key : String] : String

Gets or sets the data for **key** in the Storage.  Only
Strings may be saved in Storage. 

You can also use 
%%#getItem|**getItem()**%% to retrieve the value and
%%#setItem|**setItem()**%% to set the value.

For **keys** that are 
valid JavaScript property names, you can access the 
value by using the **storage.key** syntax.

<htmlexample>
<script>
  if (!sessionStorage.createdExamples) {
    // Set a few values
    sessionStorage.simpleKey = 'foo';
    sessionStorage['complex key!'] = 'bar';
    sessionStorage.createdExamples = 'true';

    console.log('Added examples to sessionStorage');
  }
  else {
    console.log('Using existing examples in sessionStorage');
  }

  for (var i = 0; i < sessionStorage.length; i++) {
    var key = sessionStorage.key(i);
    console.log('"' + key + '" = "' + sessionStorage[key] + '"');
  }
</script>
</htmlexample>

----
instance.length : Number

Returns the number of items saved in the Storage.

<htmlexample>
<script>
  if (!sessionStorage.createdExamples) {
    // Set a few values
    sessionStorage.simpleKey = 'foo';
    sessionStorage['complex key!'] = 'bar';
    sessionStorage.createdExamples = 'true';

    console.log('Added examples to sessionStorage');
  }
  else {
    console.log('Using existing examples in sessionStorage');
  }

  console.log(sessionStorage.length + ' items in storage');
  for (var i = 0; i < sessionStorage.length; i++) {
    var key = sessionStorage.key(i);
    console.log('"' + key + '" = "' + sessionStorage[key] + '"');
  }
</script>
</htmlexample>

ReadOnly:
true

----
prototype.key(index : Number) : String

Returns the key for the item at **index** in **this**. Use
%%#indexer_String|**this[key]**%% or %%#getItem|**this.getItem(key)**%%
to retrieve the value for the returned key.

<htmlexample>
<script>
  if (!sessionStorage.createdExamples) {
    // Set a few values
    sessionStorage.simpleKey = 'foo';
    sessionStorage['complex key!'] = 'bar';
    sessionStorage.createdExamples = 'true';

    console.log('Added examples to sessionStorage');
  }
  else {
    console.log('Using existing examples in sessionStorage');
  }

  for (var i = 0; i < sessionStorage.length; i++) {
    var key = sessionStorage.key(i);
    console.log('"' + key + '" = "' + sessionStorage[key] + '"');
  }
</script>
</htmlexample>

----
prototype.getItem(key : String) : String

Gets the data for **key** in the Storage. 

You may also use 
%%#indexer_String|**this[key]**%% to retrieve the value.

For **keys** that are 
valid JavaScript property names, you can access the 
value by using the **storage.key** syntax.

<htmlexample>
<script>
  if (!sessionStorage.createdExamples) {
    // Set a few values
    sessionStorage.simpleKey = 'foo';
    sessionStorage['complex key!'] = 'bar';
    sessionStorage.createdExamples = 'true';

    console.log('Added examples to sessionStorage');
  }
  else {
    console.log('Using existing examples in sessionStorage');
  }

  for (var i = 0; i < sessionStorage.length; i++) {
    var key = sessionStorage.key(i);
    console.log('"' + key + '" = "' + sessionStorage.getItem(key) + '"');
  }
</script>
</htmlexample>

----
prototype.setItem(key : String, value : String) : undefined

Sets the data for **key** in the Storage.  Only
Strings may be saved in Storage. 

You can also use 
%%#getItem|**getItem()**%% to retrieve the value and
%%#setItem|**setItem()**%% to set the value.

For **keys** that are 
valid JavaScript property names, you can access the 
value by using the **storage.key** syntax.

<htmlexample>
<script>
  if (!sessionStorage.createdExamples) {
    // Set a few values
    sessionStorage.simpleKey = 'foo';
    sessionStorage['complex key!'] = 'bar';
    sessionStorage.createdExamples = 'true';

    console.log('Added examples to sessionStorage');
  }
  else {
    console.log('Using existing examples in sessionStorage');
  }

  for (var i = 0; i < sessionStorage.length; i++) {
    var key = sessionStorage.key(i);
    console.log('"' + key + '" = "' + sessionStorage[key] + '"');
  }
</script>
</htmlexample>


----
prototype.removeItem(key : String) : undefined

Removes the item with the specified **key** from the storage.
You may also use the **delete storage[key]** syntax or 
**delete storage.key** syntax to remove the item.
See also %%#clear|**clear()**%%.

<htmlexample>
<button onclick='removeItems()'>Remove Items</button>
<script>
  if (!sessionStorage.createdExamples) {
    // Set a few values
    sessionStorage.simpleKey = 'foo';
    sessionStorage['complex key!'] = 'bar';
    sessionStorage.createdExamples = 'true';

    console.log('Added examples to sessionStorage');
  }
  else {
    console.log('Using existing examples in sessionStorage');
  }

  var printStorage = function() {
    console.log(sessionStorage.length + ' items in storage');
    for (var i = 0; i < sessionStorage.length; i++) {
      var key = sessionStorage.key(i);
      console.log('  "' + key + '" = "' + sessionStorage[key] + '"');
    }
  };

  var removeItems = function() {
    // The following are all equivalent ways of deleting a key
    delete sessionStorage.simpleKey;
    sessionStorage.removeItem('complex key!');
    delete sessionStorage['createdExamples'];

    printStorage();
  };
</script>
</htmlexample>

----
prototype.clear() : undefined

Removes all items from the storage. See also %%#removeItem|**removeItem()**%%.

<htmlexample>
<button onclick='clearStorage()'>Clear Storage</button>
<script>
  if (!sessionStorage.createdExamples) {
    // Set a few values
    sessionStorage.simpleKey = 'foo';
    sessionStorage['complex key!'] = 'bar';
    sessionStorage.createdExamples = 'true';

    console.log('Added examples to sessionStorage');
  }
  else {
    console.log('Using existing examples in sessionStorage');
  }

  var printStorage = function() {
    console.log(sessionStorage.length + ' items in storage');
    for (var i = 0; i < sessionStorage.length; i++) {
      var key = sessionStorage.key(i);
      console.log('  "' + key + '" = "' + sessionStorage[key] + '"');
    }
  };

  var clearStorage = function() {
    sessionStorage.clear();

    printStorage();
  };
</script>
</htmlexample>