Implementing multifile upload from stratch

I want to implement a multi file upload function for my website. When I googled for tutorials on it, I found many plugins but nothing which can guide me about how to develop it from scratch. The project I am working on is for my learning purpose so I don't want to use any plug in. I can use 开发者_Go百科I frames but flash is again not a choice for me. Can anyone help. I want some brief steps of it. Thankx.

PS. I know how to develop its back end. I want to implement its front end.

1. Start with a single <input type="file" name="file" /> field.
2. Then, to make it multiple, add a javascript function, which dynamically creates fields and add them into the page.
3. Than, to make upload without reloading page, put it all in the iframe.