Localdb.js

Introduction

Now a days you have heard of HTML5 web storage to store data locally within the user's browser. If you are not familiar with it then I am giving you a very quick introduction to it.

HTML Web Storage: when we want to store data at the client's machine we usually use cookies but HTML5 introduces the new concept called web storage that does the same thing with more security and efficiency. By using this we can store a large amount of data without affecting your website performance because this data is not included with every call to the server.

HTML5 introduces the following two mechanisms

1. localStorage: Stores data without any expiration date
2. sessionStorage: Stores data for a specific session; the data will be deleted as soon as the session ends.

Now we can explain what localDB.js is. It is a library that maps the structure of databases in objects using the localStorage API provided by HTML5. So it is compatible with all browsers that support HTML5 Web Stoage. This is completely standalone and there is no dependency except browser supporting localStorage.

There is no driver required, just add the library and use it. This library is useful for web applications, mobile apps or game engines. It has a limit of 5MB before the browser warns the user.

How To Use/Install

Download from https://github.com/mike183/localDB

And import the library

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

Structure of Database

The structure of the dabase is displayed below.



Load a database

The following will create a new database if the database is not present, otherwise it loads the existing database.

var db=new localdb(<Database Name>);

Create Table

The following will create a schemaless table, so there is no need to provide column information; simply use "g=" to provide the name of the table and it will create the table.

Db.createTable('table_name');

Delete a Table

You can delete a table by simply calling dropTable method as in the following:

Db.dropTable('table name');

Insert Data

A localDB database is schemaless so when you insert data there is no need to worry about the number of columns that you have provided in another row because each row can have it's own set of coulmns.

Db.insert('table_name',data object);

Updating database

Db.update(table_name,data_object,where_object);<br />
Db.updateById(table_name,data_object,id);

Checking for the existence of a database or table

Var res=db.tableExists('table_name');<br />
Var res=db.tableExists('users');

Exporting Database

Var json=db.exportData();<br />
Var json=db.exportData('table_name');

So that is all about the boring syntax. We will now create a sample application to understand the real use of this library.

1. Create a website in Visual Studio named demo and copy the localdb.js file that you have already downloaded.
2. Now create a webpage and import this js file as in the following:

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

3. Here I have created a First name and Last name in two textboxes and I will add both names in the database on the click of the add button and on the click of the show button it will display all the records.
   
   
   
   
   
   <table>
           <tr>
               <td>
                   First Name</td>
               <td>
                   <input id="Text1" type="text" /></td>

           </tr>
           <tr>
               <td >
                   Last Name</td>
               <td>
                   <input id="Text2" type="text" /></td>
           </tr>
           <tr>
               <td>
                   &nbsp;</td>
               <td>
   <input id="Button1" type="button" value="Add" onclick="return   Add_onclick()"/>&nbsp;&nbsp;
   <input id="Button2" type="button" value="Show" onclick="return Show_onclick()" />
   </td>
           </tr>
       </table>  
      <div id="data">
   </div>
    

4. Let's see in code how I did this.
   
   <script language="javascript" type="text/javascript"> 
           var db = new localdb('demo');
           db.createTable('users');
           function Add_onclick() {
                    db.insert('users', { 'FirstName':   document.getElementById('Text1').value,
                   'LastName': document.getElementById('Text2').value
               });
                 alert('Successfully Added"); 
           } 
           function Show_onclick() {
               var table = db.exportData('users');                      
               document.getElementById('data').innerHTML = table;
           }
   </script>
    
5. First I created a localdb named Demo and then I created 1 table. So in both the localdb and the table if it already exists then it will use the existing one otherwise create a new object.
    
6. Now on the click of the show button I have assigned an entire JSON object to the div tag to be displayed. Here I simply showed all the JSON data as it is. If you want to manipulate the data then you can easily extract the data from the JSON object.

Conclusion

There are many libraries present for storing data in a database using the localStorage API of HTML5. Here I have introduced one of them, so if you want to explore more please go through other libraries. It is really powerful since we can store data at the client side more securely and efficiently.