How to check multiple text box using java script

Dear Sir,

I am newer in asp.net 2010, I have a page which contains 10 text fields. every fields should be checked empty text or null value. but I want to use java script function which checks every text field. in that case I want to write function like 'CheckEmptyText' using js file and want to call from code behind language because i don't want to call from body in .aspx file. show how to possible please give me a hints or sample project so that I can followup the way.

In addition to that I have another question that is it necessary to check validation from both side client and server. and what is difference between client and server side validation checking.

Please assist me.

Thanking you

Debasis Bag