YUI Library Examples: Storage Utility: Advanced Storage Example

Advanced Storage Example

This example consists of two text fields, a few Buttons and a DataTable. The Buttons allow you to save data, set properties on your YAHOO.util.Storage instance, or clear all items from storage.

Once the page is drawn, initialize is called to instantiate a YAHOO.util.Storage instance and set up some listeners. We also disable all of the Buttons until the YAHOO.util.Storage instance is ready.

function initialize() {
        // evaluate and create the Storage instance
        var engineBtn = engineRadio.get("checkedButton");
        var engineType = engineBtn.get("value");
        var useSession = sessionCheckbox.checked;
        var location;

location = YAHOO.util.StorageManager[useSession ? 'LOCATION_SESSION' : 'LOCATION_LOCAL'];
        storage = YAHOO.util.StorageManager.get(engineType, location, {force: false});

storage.unsubscribe(storage.CE_CHANGE, onChange);
        storage.subscribe(storage.CE_CHANGE, onChange);
        
        if (storage.isReady || (storage._swf && YAHOO.util.StorageManager.LOCATION_SESSION === location)) {
            load();
        } else {
            saveButton.set("disabled", true); 
            purgeButton.set("disabled", true);  
            removeButton.set("disabled", true); 
            
            engineRadio.set("disabled", true);
        
            storage.subscribe(storage.CE_READY, onContentReady);
        }
    }

When storage is ready, it will dispatch a storage.CE_READY event. We can then enable the Buttons and initialize a DataTable with any previously stored values. Because items are stored as key/value pairs, we need to loop through them to turn them into name-value pairs suitable for use with the DataTable. The load function is called on page initialization and each time you switch engine options, creating or updating datatable as necessary.

function onContentReady(event) {
        saveButton.set("disabled", false); 
        purgeButton.set("disabled", false);  
        removeButton.set("disabled", false);
        
        engineRadio.set('disabled', false);
        engineRadio._buttons[0].set("disabled", ! YAHOO.util.StorageEngineHTML5.isAvailable()); 
        engineRadio._buttons[1].set("disabled", ! YAHOO.util.StorageEngineGears.isAvailable()); 
        engineRadio._buttons[2].set("disabled", ! YAHOO.util.StorageEngineSWF.isAvailable());
        
        storage.unsubscribe(storage.CE_READY, onContentReady);

load();
    }
    
    function load() {
        var len = storage.length,
            arr = [];

// clear the existing datatable
        if (datatable)
        {
            datatable.deleteRows(0, datatable.getRecordSet().getLength());
        }
            
        for (var i = 0, key, newobj; i < len; i++)
        {
            key = storage.key(i);
            newobj = { name:key, value: storage.getItem(key) };
            arr.push(newobj)
            if (datatable) {datatable.addRow(newobj);}
        }
        
        // only initialize the datatable once
        if (! datatable)
        {
            var datasource = new YAHOO.util.LocalDataSource(arr);

datasource.responseSchema = {fields : ["name", "value"]};
        
            var configs = 
            {   
                scrollable: true
            }
            
            var columns = 
            [
                {key:"name", label:"Storage Name (Key)"},
                {key:"value", label:"Text Stored"}
            ];
                
            datatable = new Yahoo.widget.DataTable("datatableContainer", columns, datasource, configs);
        }
    }

The save Button is set up to take the values from the text fields and store them, using the setItem method of storage.

Similarly, a couple of other Buttons are set up to remove items from storage, either by name or index, or by clearing the entire local store.

We've already set up a listener for a storage.CE_CHANGE event, which is dispatched whenever an item is successfully added, updated, or deleted. That calls this function, which loops through the DataTable. Using the info property of the event, we can determine what type of change occurred, and either add rows to it, delete rows from it, or update its current values.

function onChange(event) {
        //added
        if (event.type === YAHOO.util.StorageEvent.TYPE_ADD_ITEM || event.type === YAHOO.util.StorageEvent.TYPE_UPDATE_ITEM)
        {
            var newobj = {name: event.key, value: event.newValue};

var len = datatable.getRecordSet().getLength();
        
            //loop through current records and see if this has been added before
            for (var i = 0; i < len; i++ )
            {
                var rec = datatable.getRecord(i);
                var data = rec.getData();
                
                //if it's been added already, update it
                if (data.name == event.key)
                {
                    datatable.updateRow(i, newobj);
                    return;
                }
            }
    
            //if it's not been added, add it
            datatable.addRow(newobj);
        }

//removed
        else if (event.type === YAHOO.util.StorageEvent.TYPE_REMOVE_ITEM)
        {

var len = datatable.getRecordSet().getLength();
        
            //loop through current records and see if this has been added before
            for (var i = 0; i < len; i++ )
            {
                var rec = datatable.getRecord(i);
                var data = rec.getData();
                
                //if it's been added already, update it
                if (data.name == event.key)
                {
                    datatable.deleteRow(i);
                    return;
                }
            }
        }       
    }

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Storage Utility Examples:

More Storage Utility Resources:

All YUI 2.x users should review the YUI 2.8.2 security bulletin, which discusses a vulnerability present in YUI 2.4.0-2.8.1.