How to bundle and minify CoffeeScript files in .NET4.5 MVC4 with C#

In the previous blog post I showed you how the bundling and minification mechanism in MVC4 works with CSS and JavaScript files. Some of you may have CoffeeScript files in their projects and you may be wondering if they can be bundled as well. The answer is yes, and it’s not complicated at all.

Add a new folder to your MVC4 application called CoffeeScript. Add a file called to it and insert the following CoffeeScript code:

class Customer
	constructor: (@name) ->

	complain: ->
		alert @name + " says: WHERE IS MY ORDER???!!!!"

cust = new Customer("Angry customer")

This should not be too complicated I believe: we construct a Customer object and call its complain() method.

The next step is to import a package called CoffeeBundler from NuGet: PM> install-package CoffeeBundler. This will add the necessary DLLs to your projects. Now we have access to another type of bundler which will translate CoffeeScript into JavaScript and also perform the bundling and minification processes.

Next go to the BundleConfig.RegisterBundles method and add the following bit of code:

Bundle coffeeBundler = new ScriptBundle("~/bundles/coffee")
            coffeeBundler.Transforms.Insert(0, new CoffeeBundler.CoffeeBundler());

As CoffeeScript is nothing but JavaScript we still need to create a ScriptBundle object and include our CoffeeScript file in it. We also need to add a transform which will translate the CoffeeScript files into JavaScript, compile them and bundle/minify them. We also want to make sure that this is the first transformation that runs, hence the 0 in the Insert method. By default the JS bundler is the first in the transformation process.

Now let’s open _Layout.cshtml and insert the following bit of code right before the closing /body tag:

<script src="@BundleTable.Bundles.ResolveBundleUrl("~/bundles/coffee")"></script>

In case you do a build now you may receive some errors that complain about a file called AppStart_RegisterCoffeeBundler.cs. This was added automatically when we inserted the CoffeeBundler package from NuGet. You can safely delete this file; its automatically generated code had not quite caught up with .NET4.5 when writing this blog post.

The reason we use the longer script tag to call the ResolveBundleUrl instead of the shorter Scripts.Render is the same: the CoffeeBundler is a bit behind the developments in .NET4.5 and it’s safer to use the longer version.

Now run the application. If all went well then you should see a standard JavaScript alert stating that there’s an angry customer. Open the source view to check the generated HTML. You should see that the CoffeeScript bundle has been created:

<script src="/bundles/coffee?v=_Jtpxzv6QVFgvnfRHCOt5_bHmKJW0D27L4nwCa0u1gU1"></script>

Call that bundle from the browser, the address should be http://localhost:xxxx/bundles/coffee and you should see the JavaScript that the CoffeeScript bundler has generated:

(function(){var n,t;n=function(){function n(n){}return n.prototype.complain=function(){return alert(" says: WHERE IS MY ORDER???!!!!")},n}(),t=new n("Angry customer"),t.complain()}).call(this)

So, simple as that!

View the list of MVC and Web API related posts here.


About Andras Nemes
I'm a .NET/Java developer living and working in Stockholm, Sweden.

One Response to How to bundle and minify CoffeeScript files in .NET4.5 MVC4 with C#

  1. Package dependency of this post seems to be unpublished now (taken down) from nuget.

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