DOM Storage Query Language (DomSQL) is an SQL inspired interface for DOM Storage (or Web Storage as defined in the W3C working draft).

Following the basic theme of SQL, DomSQL simulates a database.table type of address system; local and session map to the localStorage and sessionStorage native objects respectively and are the database containers to which any number of tables can be bound. With the caveat that browser implementations of Web Storage have a storage limit of currently between 5 and 10mb.

How it works:

Create a table

Creating tables can be done dynamically by simply inserting into a new named table, though a stricter approach is to define a table schema manually. This has the advantage of more normalized output - only fields defined in the schema will be stored - and some added features like default values and auto incrementing fields.

// Define a table schema
DomSQL.defineTable( 'local.foo', [
   'name',
   'surname',
   'shoesize',
   'race DEFAULT "other"',
   'id AUTO_INC',
   'time TIMESTAMP'
]);

Insert some data

Inserting data into tables follows standard SQL conventions, with the addition of a convenience insert method.

Note: Keywords in statements are not case sensitive, and statements are not white-space sensitive provided all literal string are quoted.

DomSQL.query( 
   'insert into local.foo (name, surname, shoesize) '+
   'values (Jack, Jones, 12)' );

// Alternative syntax 
DomSQL.insert( 'local.foo', [{
   name: 'Jack',
   surname: 'Jones',
   shoesize: 11
},{
   name: 'Jack',
   surname: 'James',
   shoesize: 12
},{
   name: 'Jerry',
   surname: 'Springer',
   shoesize: 10
},{
   name: 'Chuck',
   surname: 'Norris',
   shoesize: 14
}]); 

Query data

Limited SQL features are supported in query statements, including selecting return fields, nested WHERE/AND/OR, ORDER BY and LIMIT.

Each result set is a JavaScript Array of Object literals, with the addition of some 'sugar' methods.

var result = DomSQL.query(
   'SELECT name, surname FROM local.foo '+
   'WHERE shoesize >= 10 AND ( name != "Chuck" OR surname != "Norris" )'+
   'ORDER BY name, shoesize DESC'
);

// Print result to console
result.log();
/*
>>>
[0]
   name: 
      Jack
   surname:
      James
[1]
   name:
      Jack
   surname:
      Jones
[2]
   name:
      Jerry
   surname:
      Springer
*/

Update and delete data

Familiar SQL syntax is available for updating and deleting rows of data:

DomSQL.query( 'delete from local.foo where surname = ?', ["Springer"] )

DomSQL.query( 'update local.foo set shoesize = 15 where name = :name', { 'name' : "Chuck" } )

Working with result sets

Query result sets have some added convenience methods:

// Set localStorage as the default database
DomSQL.useLocal();

var query = DomSQL.query( 'select * from foo' );

// Iterate
query.each( function ( row ) {
   //...statements
});

// Send formatted output to console
query.log();

// Invoke custom toString method (Not available in IE)
alert( query );

Support:

Support for the Web Storage API is quite strong encompassing all the latest releases from the main browsers; Internet Explorer, Firefox, Safari, Opera and Chrome.

The DomSQL object is not added to the page if web storage is not natively available, so a simple check for support is as simple as:

if ( window.DomSQL ) {
   // ...statements
}  

Dependencies:

This script is standalone, and requires no other JavaScript libraries.

Demonstration:

A simple image to data URI converter that uses DomSQL to keep a locally stored record of converted images:
http://tools.the-echoplex.net/img-data-uri/