[1] Touch Events ( ( 版)) <https://dvcs.w3.org/hg/webevents/raw-file/v1/touchevents.html#touchlist-interface>
[2] TouchList Class Reference ( ( 版)) <https://developer.apple.com/library/safari/documentation/UserExperience/Reference/TouchListClassReference/TouchList/TouchList.html#//apple_ref/doc/js_ref/TouchList>