To include multiple js files in page is bad in terms of http request. Yslow Yahoo! tool can give you bad grade. Grade F on making more HTTP requests.
Apart from that page loading time increases and page does not looks clean.

Combined files are a way to reduce the number of HTTP requests by combining all scripts into a single script, and similarly combining all CSS into a single stylesheet.

Including multiple .js file in one external file has several advantages.
1. Less HTTP request.
2. If cashing is on page lode faster.
3. Page looks clean.

Use this code to add as much as files as you want.

document.write('');
document.write('');
document.write('');
document.write('');