how to write coding in javascript

Are you sure you know what language you are working in? To my knowledge, JavaScript does not hold permanent data, hence, it is not a data base system. Secondly, unless someone is absolutely clueless about how to access the code, your password thingy doesnt make a whole lot of sense. You could try a cookie thing, and you could try encoding certain things, over, and beyond that, i dont think JavaScript is what you are looking for.

Perhaps if you could paste the code, or tell others what you have in mind, you will get a better response.

Do you mean a login system to access restricted parts of your website?

you'll just have to learn any of the following: JSP, ASP, PHP, Perl, ColdFusion, or htaccess. furthermore, your host server must be setup to use it. geocities, etc don't.