As far as I know you cannot really disable error checking (if that is what you're asking), if your code is broken.. fix it.
However you can disable so called "hints" for Javascript.
You can find this option in the tools menu (found under "options").
In the top menubar choose "editor" and go to the "hint" tab.
In the language dropdown select Javascript. You will see a list of warnings which you can disable.
You can however disable syntax highlighting, this is found in the same menu but under the option "fonts & colors" and the tab "highlighting". However you cannot choose for which language you want to do this.