jsormdb--an Embedded JavaScript Database

The jsormdb library introduces several concepts and implementations that are necessary for creating and using a database. Note that all of these are detailed in the JavaScriptDoc distributed with jsormdb, in the doc folder.

Putting it all together, you can create a database instance JSORM.db.db that retrieves data via HTTP from your server using JSORM.db.channel.http and parses it in JSON format using JSORM.db.parser.json. Figure 3 shows how all the pieces work together.

Figure 3. Fetching and Parsing Data from the Server

It is important to note that all classes follow Douglas Crockford's principles and are instantiated directly, without the “new” keyword:

var parser = JSORM.db.parser.json();     // right
var parser = new JSORM.db.parser.json(); // WRONG!

As much as possible, jsormdb semantics follow those of classical SQL. Thus, adding records is an insert; modifying records is an update, and so forth.

Installing jsormdb involves a few simple steps.

1) Download and unzip the library from the jsorm site, where it is available as a zip file from the Download link.

2) Install the library. The download includes two versions of the library. jsormdb.js is minified at just under 25KB. jsormdb-src.js is not minified, is used primarily for debugging and is 77KB. You can reduce their sizes further with gzip. You need to install the library you want to use in a path accessible to your browsers. For the purposes of this example, install file jsormdb.js in the same directory as your Web page.

3) Include the library in your Web page. Normally this is done in the header as follows:

<script type="text/javascript" src="jsormdb.js"></script>

Now that you have downloaded and installed the library, as well as included it in your page, you are ready to create a database.

In the simplest form, you create a database by simply instantiating it:

var db = JSORM.db.db();

Although this creates a database, you may want to add some initial configuration parameters. For example, you may want to indicate the parser and/or the channel to use, or even to load some data directly.

jsormdb supports loading data in two ways: directly, using raw data, and remotely, via a channel:

var conf, db;
// to use a channel and parser
conf = {
    channel: JSORM.db.channel.http({updateUrl: "/send/text.php",
                                    loadUrl:   "/receive/text.json"}),
    parser:  JSORM.db.parser.json()
}
db = JSORM.db.db(conf);

// to load data directly
conf = {data: [{name: "Joe",   age: 25},
               {name: "Jill",  age: 30},
               {name: "James", age: 35}]}
db = JSORM.db.db(conf);

JSORM.db.db has many options for instantiation. See the API docs or the Wiki entry, both of which are listed in the Resources for this article.

Whichever manner you choose to load data, jsormdb expects the data passed to it to be an array of simple JavaScript object literals. jsormdb is not rigid about the data structure, and it does not care what fields exist on each object. Both of the following are equally valid:

data = [{name: "Joe",   age: 25},
        {name: "Jill",  age: 30},
        {name: "James", age: 35}];

data = [{name:      "Joe",   age:  25},
        {firstName: "Jill"},
        {surname:   "James", city: "London"}];

An important note about the records is that each can have a type. When a record has a type, it is specially marked and can be searched more easily along with others of the same type. This can improve search times greatly, akin to putting records in different tables in an RDBMS:

data = [
	{name: "Joe",     age: 25,         type:   "person"},
	{name: "Jill",    age: 30,         type:   "person"},
	{name: "James",   age: 35,         type:   "person"},
	{name: "Fiat",    color: "yellow", type:   "car"},
	{name: "Ferrari", color: "red",    type:   "car"},
	{name: "GM",      color: "white",  type:   "car",
	                                   status: "bankrupt"}
	];