Image voting system using jQuery, Bootstrap and Asp.Net MVC 3, or how to create a jQuery plugin


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I was working on a project were one of the requirements was that users had to select a set of images out of a bunch of them, to be furtherly reviewed and commented.
While working on the implementation, I had a sudden idea: I’m going to write for my blog a simple image voting system packed as a jQuery plugin! And so iLikeIt! was born.
The link between the project and the blog article has been Twitter’s Bootstrap, and precisely the Carousel component, as I was using it to iterate between the images.

Live demo and source code

I’ve always wanted to be able to offer live demos of my web applications, and I finally found a fantastic (free) app hosting, appharbor, which also integrates perfectly with Github, so that when I push my changes to Github, it automatically pushes them to appharbor and the new version gets immediately and automatically deployed
on the server!
Click to reach the live demo of iLikeIt!
As always my code is hosted on Github and is free to fork, download etc… (link).

iLikeIt! Screenshot

iLikeIt! screenshot

What iLikeIt! is

iLikeIt! is a simple image voting system that can be used as a classic jQuery plugin, using Bootstrap and jQuery (of course) as base components, and Asp.Net MVC 3 as the web framework to handle server side computation, even though the server side part is really less important here.
The vote is visually expressed with classic “stars” icons, and is 5-stars based.

UI and UX

The idea is to keep the page simple, focusing only on the images and the voting system.
The image rotation is based on a carousel styled component, and to cast a vote a user simply has to mouse over the image and the panel to vote will fade in in the middle of the image, allowing the user to rate the image by clicking on a star.
After the user has casted his vote, the system will display the average rating for the image and won’t allow the user to change his vote (or not until the user refreshes the page… ehi I told you this is a simple system, but you’re free to modify it by cloning and adapting the source code to your needs!).
I know mouse over is not good this days due to mobile experience, and that’s why I will try and cover this topic (and fix the design) in one of my next post.

How to

The HTML part

I wanted the plugin to be dead simple to use, with a jQuery classic approach such as $(“…”).myPlugin().
In the following Gist you can see the HTML code of the View that is needed to use iLikeIt!

The main idea is that from the HTML point of view, all that is needed is to setup the Bootstrap’s Carousel component filled in of all the images you need (if you don’t know about Bootstrap and how to setup a Carousel, please read this ).
It is very important to specify the IDs of the images, as they will be posted to the server to identify the image being voted!
Then, at the bottom of the page, in the script portion, we need to initialize the plugin simply writing

As you can see I’m passing an object called options to the plugin, which contains the URL used for Ajax POST actions to the server.

The javascript part

The baisc idea is to display a small div in the middle of the carousel, between the controls for sliding the images, where we display the star icons and the rating description, so that the user is facilitated when voting.
Here is the js file, which I’ll be covering in more detail immediately after:

The code is contained within an anonymouse closure, thus granting privacy and state throughout the lifetime of the application. You may notice that at the top there is a small bit of code commented out, that is because at the beginning I had decided to use the Module pattern ( and, but then I chose to simplify the usage of the plugin and changed my mind for anonymouse closure.
The usage of iLikeIt! as a jQuery plugin is possible because of the following code block

where I add iLikeIt to the set of functions that is possible to access using jQuery “$” notation.
When called, this function creates and injects the HTML to display the voting panel into the Carousel, and then hooks up all the events that are needed, like mouseenter for the voting panel, mouseover, mouseout and click for the star icons.
Whenever a user goes with the mouse over a star icon, a mouseover event will be triggered and handled by the function displayRating

which retrieves the active image (using the “active” class attribute that Bootstrap places on the current carousel item) and checks if the image has not yet been voted (more on that later). If that’s the case, then the this function is going to replace all the necessary empty icons with the full star icon, thus providing a visual feedback to the user, along a short text description of the current vote. To easily do this I enumerated the IDs of the star icon with a crescent numbering: the first, that corresponds to vote “1”, has an ID = “1” and so on till 5.
When the user has made up his mind, he can click on the icon that better expresses his thoughts about the image and the mouse event “click” will be triggered and handled by the function registerVote

This function performs an Ajax POST to the server, sending out the ID of the image and the string representation of the vote.
On success, we need to mark this image as “already voted”, and to do this I’m using the jQuery function “data()”“vote”, msg);
where msg holds the average rating that is sent back with the server response, and this value is displayed to the user by calling the preloadRating function.
I think this covers pretty much everything that is important.
The server side code is really short and not significant, but should you want to take a look at that, you can download the source.


We have seen how to create a simple jQuery plugin to build a simple image voting system, and how to use the anonymous closure construct to isolate and organize your javascript code.

Have fun,