javascript event which

Returns a value relevant to the type of event. For mouse events, the property value is an integer indicating which mouse button was used (1 is the left button; 3 is the right button). For keyboard events, the property value is an integer of the keyboard character ASCII code. This property survives in Netscape 6 as a carryover from the Navigator 4 event model. Use the button, charCode, and keyCode properties if you no longer need to support Navigator 4.