This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.
var buttonPressed = instanceOfMouseEvent.which
A number representing a given button:
0: No button
1: Left button
2: Middle button (if present)
3: Right button
For a mouse configured for left-handed use, the button actions are reversed. In this case, the values are read from right to left.
This is not part of any specification.
|Feature||Edge||Firefox (Gecko)||Chrome||Internet Explorer||Opera||Safari|
|Basic support||(Yes)||1.0 (1.7 or earlier)||1.0||9.0||5.0||1.0|
|Feature||Edge||Firefox Mobile (Gecko)||Android||IE Mobile||Opera Mobile||Safari Mobile|
|Basic support||(Yes)||1.0 (1) ||(Yes)||(Yes)||(Yes)||(Yes)|