The MouseEvent.clientX read-only property provides the horizontal coordinate within the application's client area at which the event occurred (as opposed to the coordinates within the page). For example, clicking in the top-left corner of the client area will always result in a mouse event with a clientX value of 0, regardless of whether the page is scrolled horizontally.
The MouseEvent.clientY read-only property returns the vertical coordinate within the application's client area at which the event occurred (as opposed to the coordinates within the page). For example, clicking in the top-left corner of the client area will always result in a mouse event with a clientY value of 0, regardless of whether the page is scrolled vertically.
The MouseEvent.movementX read-only property provides the shift in the X coordinate of the mouse pointer between that event and the previous mousemove event. In other words, the value of that property is computed that way : currentEvent.movementX = currentEvent.screenX - previousEvent.screenX.
The MouseEvent.movementYread-only property provides the shift in the Y coordinate of the mouse pointer between that event and the previous mousemove event. In other words, the value of that property is computed that way : currentEvent.movementY = currentEvent.screenY - previousEvent.screenY.