Introduction to IndexedDB

Introduction

 

As the name implies, IndexedDB is a database in which we can do all kinds of operations we do in a normal database. This IndexedDB has been introduced with Html. This allows a user to store large amounts of data in their browser. It has been proved that IndexedDB is more powerful and efficient than other storage mechanisms like local storage and session storage. Basically IndexedDB is an API that helps the developers to do some database operations on the client-side, like creating a database, opening the transaction, creating tables, inserting values to tables, deleting values, and reading the data. If you need any other way to save some data on the client-side, you can use storage mechanisms introduced in HTML5. Now we will look at some of the operations a developer can do with IndexedDB. I hope you will like this.

 

Background

 

Before introducing IndexedDB, developers were familiar with Web SQL.

 

Why use IndexedDB instead of Web SQL

 

W3C has announced that the use of Web SQL is obsolete and deprecated, hence it is not recommended to use Web SQL in your applications. Most of the modern web browsers like Mozilla do not support the use of Web SQL, this is also a great limitation of Web SQL.

 

Now we have an alternative to Web SQL, IndexedDB, which more efficient and faster than Web SQL. The following are some of the main advantages of IndexedDB.

• It stores the data as Key-Pair values
• It is asynchronous
• It is non-relational
• Can access the data from the same domain

Using the code

 

As you all know, the first step to work with a database is just creating it.

 

Create/Open IndexedDB Database

 

It is always better to check whether your browser supports IndexedDB or not. To check that you can use the following syntax:

<script type="text/javascript">
window.indexedDB = window.indexedDB || window.mozIndexedDB || window.webkitIndexedDB || window.msIndexedDB;
//check whether the database is created or not.
if (!window.indexedDB)
{
    alert("Oops, Does not support IndexedDB");
}
</script>

So if your browser supports IndexedDB, you are ready to go! Cool! Now we can create a database.

//check whether the database is created or not.
if (!window.indexedDB)
{
    alert("Oops, Does not support IndexedDB");
}
else
{
    //Create database
    var dbName = 'myDB'; // Database name
    var dbVersion = 2; // Database version
    var crDB = window.indexedDB.open(dbName, dbVersion);
}

Here the first parameter is the database name and the second one is the version of your database. A version represents your database current schema. If everything goes well, you can see your database in your browser resources as follows.

 

 

IndexedDB Creation

 

When you create a database some certain events are fired, they are:

• onupgradeneeded

  crDB.onupgradeneeded = function (event)
  {
      alert("That's cool, we are upgrading");
      db = event.target.result;
      var objectStore = db.createObjectStore("UserName",
      {
          keyPath: "UserID"
      });
  };

  This event gets fired when you try upgrading your database. Here we are creating an object store with the name ‘UserName’ and index key ‘UserID’. The following is the output you get when the onupgradeneeded is fired.
   
   
  IndexedDB onupgradeneeded Alert
   
   
  IndexedDB onupgradeneeded Output
   
• onsuccess

  crDB.onsuccess = function (event) {
     alert("Awesome, You have successfully Opened a Databse!");
     db = event.target.result;
  }

  If there are no errors, you will get an alert as follows.
   
   
  IndexedDB OnSuccess Alert 
   
• onerror

  crDB.onerror = function (event) {
     alert("Oops, There is error!", event);
  }

  Here crDB is our database instance. Once this is done, we can start using the transaction as we use in SQL.

Creating transaction

 

To create a transaction we can use the following syntax. We can use the transaction method from our database instance.

//Creating transaction
var myTran = db.transaction(["UserName"], "readwrite");
myTran.oncomplete = function (e)
{
    alert("Awesome, Transaction is successfully created!");
};
myTran.onerror = function (e)
{
    alert("Oops, There is error!", e.message);
};

Here db is our database instance. And myTran is our transaction object which we are going to use for our upcoming operations. We are creating a transaction with read-write permission, that is why we have given property as ‘readwrite’ while creating a transaction. Why we use the transaction is, as you all know transaction can be rollbacked. For example, if any of the operations throws an error, the transaction will be rolled back so there won’t be any kind of mismatching data happening. And of course, we can easily manage error logs with the help of transaction. Shall we write queries needed for our operations?

 

Adding the data

 

Once our transaction is ready we can insert some data to our object in the transaction on success event, which we have called inside of database onsuccess event. Please check the below code.

crDB.onsuccess = function (event)
{
    alert("Awesome, You have successfully Opened a Databse!");
    db = event.target.result;
    //Creating transaction
    var myTran = db.transaction(["UserName"], "readwrite");
    myTran.oncomplete = function (e)
    {
        alert("Awesome, Transaction is successfully created!");
    };
    myTran.onsuccess = function (e)
    {
        alert("Awesome, Transaction is successfully created!");
        //Adding the data
        var myObj = myTran.objectStore("UserName");
        var myNames = ["Sibi", "Aji", "Ansu", "Shantu", "Aghil"]; //Array with names
        for (var i = 0; i < 5; i++)
        { //Adding 5 objects
            myObj.add(
            {
                UserID: 'SBKL0' + i,
                Name: myNames[i]
            });
        }
    };
    myTran.onerror = function (e)
    {
        alert("Oops, There is error!", e.message);
    };
}

Here myNames is the array in which we have few names and we are using a loop to insert few data to the object. Now you can see that your data have been added to the object in your browser resources.

 

 

IndexedDB Adding Data To Objects

 

We have successfully added data, right? Now we will see how to remove the data we just added.

 

Removing the data

 

If there is adding, there should be deleting. You can delete an object from object store as follows.

setTimeout(function () {
   db.transaction(["UserName"], "readwrite").objectStore("UserName").delete('SBKL00');
}, 10000);

So you can re write the on success event of transaction as follows.

myTran.onsuccess = function (e)
{
    alert("Awesome, Transaction is successfully created!");
    //Adding the data
    var myObj = myTran.objectStore("UserName");
    var myNames = ["Sibi", "Aji", "Ansu", "Shantu", "Aghil"]; //Array with names
    for (var i = 0; i < 5; i++)
    { //Adding 5 objects
        myObj.add(
        {
            UserID: 'SBKL0' + i,
            Name: myNames[i]
        });
    }
    setTimeout(function ()
    {
        db.transaction(["UserName"], "readwrite").objectStore("UserName").delete('SBKL00');
    }, 10000);
};

It can give you an output as follows.

 

 

IndexedDB Deleting Data From Objects

 

Now we will see how to access particular data from the object-store.

 

Access the data with key

 

To access particular data, we will add a button and in the button click event, we will fetch the details needed as a request.

<input id="btnGet" type="button" value="Get Name" />

Click event is as follows.

$(function ()
{
    $('#btnGet').click(function ()
    {
        var get = db.transaction(["UserName"], "readwrite").objectStore("UserName").get('SBKL01');
        get.onsuccess = function (event)
        {
            alert("The name you have requested is : " + get.result.Name);
        };
    });
});

You can get the alert as follows, if you run your code.

 

 

IndexedDB Get The Data With Key

 

Now we will see how we can update data with the Get method.

 

Updating the data

 

To update the data we will have a button and in the button click, we will fire the needed code.

<input id="btnUpdate" type="button" value="Update Name" />

And click event is as follows.

$('#btnUpdate').click(function ()
{
    var updObject = db.transaction(["UserName"], "readwrite").objectStore("UserName");
    var upd = updObject.get('SBKL03');
    upd.onsuccess = function (event)
    {
        upd.result.Name = 'New Name';
        updObject.put(upd.result);
    };
});

Here we are getting an element using the get method, and we are updating the value in the result, once it is done, we will assign that new result to the object store using put method.

 

It will give you an output as follows.

 

 

IndexedDB Update The Data With Key

 

Another interesting thing is, we can use cursors also as we use in SQL if we need to loop through some data. Here I will show you how we can do that.

 

Using Cursor

 

Create a button and write a few lines of code as follows.

<input id="btnShow" type="button" value="Show the data" />

Then we will create an HTML table.

<div id="myTab">
    <table id="show">
        <thead>
            <th>User ID </th>
            <th>Name</th>
        </thead>
        <tbody></tbody>
    </table>
</div>

Now we can write the cursor as follows.

$('#btnShow').click(function ()
{
    var curObject = db.transaction(["UserName"], "readwrite").objectStore("UserName");
    curObject.openCursor().onsuccess = function (event)
    { //Opening the cursor
        var cur = event.target.result;
        if (cur)
        { // Checks for the cursor
            $('#show').append('<tr><td>' + cur.key + '</td><td>' + cur.value.Name + '</td></tr>');
            cur.continue();
        }
    };
    $('#myTab').show();
});

Here we are creating a cursor using the function openCursor() and in the onsuccess event we are looping through the cursor. You can always give some styles to your table.

<style>
    table,
    tr,
    td,
    th {
        border: 1px solid #ccc;
        border-radius: 5px;
        padding: 10px;
        margin: 10px;
    }
</style>

That is all. Now when you click the show button, you can see the data in a table format as follows.

 

 

IndexedDB Using Cursor

 

Complete code

<!DOCTYPE html>
<html>

    <head>
        <title>Introduction to IndexedDB</title>
        <script src="Scripts/jquery-1.11.1.min.js"></script>
        <script type="text/javascript">
        var dbName = 'myDB'; // Database name
        var dbVersion = 2; // Database version
        var crDB;
        var db;
        window.indexedDB = window.indexedDB || window.mozIndexedDB || window.webkitIndexedDB || window.msIndexedDB;
        //check whether the database is created or not.
        if (!window.indexedDB)
        {
            alert("Oops, Does not support IndexedDB");
        }
        else
        {
            //Create database
            crDB = window.indexedDB.open(dbName, dbVersion);
            var db;
            crDB.onerror = function (event)
            {
                alert("Oops, There is error!", event);
            }
            crDB.onupgradeneeded = function (event)
            {
                alert("That's cool, we are upgrading");
                db = event.target.result;
                var objectStore = db.createObjectStore("UserName",
                {
                    keyPath: "UserID"
                });
            };
            crDB.onsuccess = function (event)
            {
                alert("Awesome, You have successfully Opened a Databse!");
                db = event.target.result;
                //Creating transaction
                var myTran = db.transaction(["UserName"], "readwrite");
                myTran.oncomplete = function (e)
                {
                    alert("Awesome, Transaction is successfully created!");
                };
                myTran.onsuccess = function (e)
                {
                    alert("Awesome, Transaction is successfully created!");
                    //Adding the data
                    var myObj = myTran.objectStore("UserName");
                    var myNames = ["Sibi", "Aji", "Ansu", "Shantu", "Aghil"]; //Array with names
                    for (var i = 0; i < 5; i++)
                    { //Adding 5 objects
                        myObj.add(
                        {
                            UserID: 'SBKL0' + i,
                            Name: myNames[i]
                        });
                    }
                    setTimeout(function ()
                    {
                        db.transaction(["UserName"], "readwrite").objectStore("UserName").delete('SBKL00');
                    }, 10000);
                };
                myTran.onerror = function (e)
                {
                    alert("Oops, There is error!", e.message);
                };
            }
        }
        $(function ()
        {
            $('#myTab').hide();
            $('#btnGet').click(function ()
            {
                var get = db.transaction(["UserName"], "readwrite").objectStore("UserName").get('SBKL01');
                get.onsuccess = function (event)
                {
                    alert("The name you have requested is : " + get.result.Name);
                };
            });
            $('#btnUpdate').click(function ()
            {
                var updObject = db.transaction(["UserName"], "readwrite").objectStore("UserName");
                var upd = updObject.get('SBKL03');
                upd.onsuccess = function (event)
                {
                    upd.result.Name = 'New Name';
                    updObject.put(upd.result);
                };
            });
            $('#btnShow').click(function ()
            {
                var curObject = db.transaction(["UserName"], "readwrite").objectStore("UserName");
                curObject.openCursor().onsuccess = function (event)
                { //Opening the cursor
                    var cur = event.target.result;
                    if (cur)
                    { // Checks for the cursor
                        $('#show').append('<tr><td>' + cur.key + '</td><td>' + cur.value.Name + '</td></tr>');
                        cur.continue();
                    }
                };
                $('#myTab').show();
            });
        });
        </script>
        <style>
        table,
        tr,
        td,
        th {
            border: 1px solid #ccc;
            border-radius: 5px;
            padding: 10px;
            margin: 10px;
        }
        </style>
    </head>

    <body> <input id="btnGet" type="button" value="Get Name" /> <input id="btnUpdate" type="button" value="Update Name" /> <input id="btnShow" type="button" value="Show the data" />
        <div id="myTab">
            <table id="show">
                <thead>
                    <th>User ID </th>
                    <th>Name</th>
                </thead>
                <tbody></tbody>
            </table>
        </div>
    </body>

</html>

That is all. We did it. Have a happy coding.

 

Conclusion

 

Did I miss anything that you may think is needed? Did you try Web SQL yet? Have you ever wanted to do this requirement? Did you find this post useful? I hope you liked this article. Please share your valuable suggestions and feedback.

 

Want to learn more about IndexedDB, contrinue here: HTML 5 IndexedDB Database 

 

Your turn. What do you think?

 

A blog isn’t a blog without comments, but do try to stay on topic. If you have a question unrelated to this post, you’re better off posting it on C# Corner, Code Project, Stack Overflow, Asp.Net Forum instead of commenting here. Tweet or email me a link to your question there and I’ll definitely try to help if I can.