In the below code addEventListener takes a function as parameter. My question is where can I find the documentation for the evt.x and evt.y notations.

canvas.addEventListener("click", getCoords);

function getCoords(evt){
    console.log(evt.x, evt.y);
    }

I saw in another stackoverflow question that instead of a canvas when the window object used the evt.x becomes evt.clientX and evt.y becomes evt.clientY

window.addEventListener("click",function(evt){
    console.log(evt.clientX , evt.clientY );
});