非标
此特征是非标准的，且不在标准轨道中。不要在面向 Web 的生产站点中使用它：它不适用于每个用户。实现之间可能存在大的不兼容性，且行为将来可能改变。
MouseEvent.WEBKIT_FORCE_AT_MOUSE_DOWN
is a proprietary, WebKit-specific, static numeric property whose value is the minimum force necessary for a normal click.
因为
WEBKIT_FORCE_AT_MOUSE_DOWN
is a static property of
MouseEvent
, you always use it as
MouseEvent.WEBKIT_FORCE_AT_MOUSE_DOWN
, rather than as a property of a
MouseEvent
实例。
Not part of any specification. Apple has a description at the Mac Developer Library .
