As typeof returns "object"..
var MyBlob = new Blob(['test text'], {type : 'text/plain'});
console.log(typeof MyBlob) // "object"
is it too early to ask for a generic solution for checking whether or not a variable is a blob as it is not yet widely supported? Or how should I go about testing for blob type in browsers which already have it implemented?
You can test if it is an instanceof Blob like this:
var MyBlob = new Blob(['test text'], {type : 'text/plain'});
document.body.innerHTML = MyBlob instanceof Blob;
This will work for things that inherit from Blob also.