Click on canvas - how to get coordinates correctly?

Question

JavaScript

The question is generally obvious, but I did not find a convenient code (I'm just a fan of programming in JavaScript)
Regarding the window and the document, the coordinates are obtained easily. How about canvas?

Answer 1

x = pageY - canvasElement.offsetLeft;
y = pageX - canvasElement.offsetTop;
where pageY and pageX are coordinates relative to the document.

Answer 2

msdn.microsoft.com/en-us/library/ms530302%28VS.85%29.aspx is a good article on MSDN about sizes and coordinates. Better than this on the net did not meet.