mouse x position over canvas element toggles event

mouse x position over canvas element toggles event

I can't figure out how to get the x coordinates of mouse position over a canvas element to fire en event 

example
 $("#div").fadeIn();

a simple example of how I'd like to use this function is if the mouse position is on the left of the canvas it fades a separate div in and then if the mouse is moved to the right side of the canvas element the div fades out. The canvas element is responsive and will resize with the browser 

I need the event to occur without any click event but rather on mouseOver