JS judgment by mouse and buttons

the mouse button is determined in Js.
ie
left click window . event . button = 1
right-click window . event . button = 2
window . event . button = 4
no buttons window . event . button = 0

firefox
the left button is event . button = 0
right-click event . button = 2
the key is event . button = 1
no button action event . button = 0

opera 7.23/7.54
the left mouse button is window . event . button = 1
no buttons window . event . button = 1
the right-click and Middle-click buttons cannot be obtained.

Opera 7.60/8.0
The left mouse button isWindow.Event.Button = 0
No button actionWindow.Event.Button = 0
Right-click and Middle-click cannot be obtained

In addition, the right-click blocking isWindow.Event.Button = 3