var prova = document.getElementById("prova2");
let provaBez = prova.getBoundingClientRect();

var prova2 = document.getElementById("prova");
let provaBez2 = prova2.getBoundingClientRect();

let x1 = provaBez.left;
let y1 = provaBez.top;
let x2 = provaBez2.left;
let y2 = provaBez2.top;

console.log(x1,y1, 200, 100,  x2, y2)

var c = document.getElementById("myCanvas");
    var ctx = c.getContext("2d");
    ctx.canvas.width  = window.innerWidth;
    ctx.canvas.height = window.innerHeight;
    ctx.beginPath();





    ctx.bezierCurveTo(x1,y1, 200, 100,  x2, y2);


    ctx.stroke();