CODE EXAMPLE FOR JAVASCRIPT

check if type is blob javascript

You can test if it is an instanceof Blob like this:

var MyBlob = new Blob(['test text'], {type : 'text/plain'});
console.log(MyBlob instanceof Blob) // true
jsFiddle: http://jsfiddle.net/jfriend00/5xkgd/

This will work for things that inherit from Blob also.