I want to start developing a library in javascript. I have looked at various design patterns and bundlers.

I came across UMD design pattern, haven't understood it in detail. Can someone provide me with some resources to understand UMD in depth or an explanation here too would be great.

Mainly about this

function(root, factory){
    // code goes here
}()

What is root and factory in the above.

Then how to use bundlers in the end.

I also understand it is a very elaborate question, but I really can't find any material online that explains exactly what the above does.

Any help is much appreciated....thanks !!