it is coded in vanilla javascript. i do nothing to cater IE9, it just run well. btw, believe there are some scenarios to load page within IE9 (e.g. OLE control, hta script)
FWIW there's nothing about "vanilla JavaScript" that means IE9 will be supported. It's avoiding certain language features and DOM APIs that does it.
Just adding this because it can lead to the implication that not supporting IE9 means you're trying to do something frivolous as opposed to "vanilla JavaScript".