Can we use the JS SDK for building Canvas Application?

The answer is "YES". Simply remember to configure your application settings to use "IFrame" as the render method.

 

What are the Differences between Using the JavaScript SDK to Build Canvas Application and Connect Websites?

Technically speaking, while the canvas application that uses the JavaScript SDK will be embedded in an iframe while it appears in Facebook pages, using the JavaScript SDK to build canvas application and integrate Facebook on websites are very similar.

One of the major issues that you should consider is probably the differences in the look-and-feel and user experience between using canvas applications and external websites. For example,

As an example, if we run our "Our 1st FB App (JS SDK)" as an canvas application instead of in its own external website, the display layout simply does not fit in as a Facebook page.

Facebook dashboard header

 

So, in migrating "Our 1st FB App (JS SDK)" to run as a canvas migration, the page layout will be changed as shown below.

Facebook dashboard header

 

It looks much better, right?