I just noticed this thread. I've got a bit of Java under my collar, but not much. (Think two weekends with a textbook.) I can only run a bit of question&answer with popup windows, so this is pretty high-level stuff to me.
But that's not important. My opinion: Certification = Yes. Always good to have it say on your resume/website 'Certified Java programmer with X years of focused experience."
EDIT: Nice name, davidy22. Spoken with pure programming evil.
Javascript is different from java. Java runs on a bytecode interpreter, and needs to be compiled. Javascript runs inside a browser and needs no compile. Javascript also tends to run much slower than java, because of the browser overhead and the need to parse in real-time.
A certification certainly helps, but isn't necessary to get a job in programming. Many firms will want to personally test your aptitude with programming problems. In those cases, practice and prior experience are needed. They may also want to see what past work you have done, thus my suggestion to work on summer of code. Helping an existing project, logging all the code you write, will contribute to that portfolio. A certification may help you get past the initial screening though.
Naming my variable that is probably poor programming practice, but I'm probably never going to touch it again and it makes for a good joke.