The MouseEvent interface is defined in the W3C Document Object Model (DOM) Level 2 Events Specification. (Refer to http://www.w3.org/TR/2000/REC-DOM-Level-2-Events-20001113.)

The MouseEvent interface provides specific contextual information associated with Mouse events.

The detail attribute inherited from UIEvent indicates the number of times a mouse button has been pressed and released over the same screen location during a user action. The attribute value is 1 when the user begins this action and increments by 1 for each full sequence of pressing and releasing. If the user moves the mouse between the mousedown and mouseup the value will be set to 0, indicating that no click is occurring.

In the case of nested elements mouse events are always targeted at the most deeply nested element. Ancestors of the targeted element may use bubbling to obtain notification of mouse events which occur within its descendent elements.