To get the width and height of an HTML5 canvas with JavaScript, we use the getBoundingClientRect method.
For instance, we write
const canvas = document.getElementById("mycanvas");
const width = canvas.width;
const height = canvas.height;
const canvasW = canvas.getBoundingClientRect().width;
const canvasH = canvas.getBoundingClientRect().height;
to select the canvas with getElementById.
And then we call getBoundingClientRect method to return an object with the width and height of the canvas.
