jQuery safer form

I'm designing a registration form for a website, and was originally going to put a captcha on it to prevent spammers posting information to it remotely. But then I found this article about safer forms using jQuery: http://15daysofjquery.com/safer-contact-forms-without-captchas/11/

I was just wondering how this is working? If a spammer remotely accesses the form, will not the javascript add the hidden field to his form as well?开发者_JS百科 Or will this only happen when the user loads the form in his browser...?

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Most bots are quite primitive and don't recreate a browser's environment - they will just parse the HTML.