How to get the Blob of the inner file?

After reading the readme.md, I don't understand how to get the Blob of the inner file yet.
Too ashamed.
Question 1: To need dataview-extra.js and reader.js or not?
Question 2: Please extend the following code, teach me how to get the Blob, thank you!!

var archive = RarArchive(file, function(err) {
if(err) {
return;
}
// Use archive
});