@sunfighter thanks for pointing out my mistake :P i never really practiced per chapter, i just read it all and then moved to next chapter, thinking i will use all that i had learned when i start making a real practice, but as they say, practice makes a man perfect, also i had tried type = number method, it wasn't working still, and i would like to thank devnull69 again, coz his method worked properly, i aint really good at DOM....
@felgall thanks for telling me the other website to learn JavaScript From, i greatly appreciate it