TamperMonkey script to help find vertices of CSS clip-path: polygon() function for CSS drawing

vertexFinder.js

// ==UserScript==
// @name         vertexFinder
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  logs clicked vertex coordinates in parent element percentages to console for CSS polygon clip-path
// @author       Brian Mosher
// @match        https://mosherbrian.github.io/*
// @icon         data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==
// @grant        none
// ==/UserScript==
function roundToTwo(num) {
    return +(Math.round(num + "e+2")  + "e-2");
}

function vertexFinder(e)
{
    //console.log(e.target);
    const { offsetWidth: parentWidth, offsetHeight: parentHeight, offsetLeft: parentLeft, offsetTop: parentTop } = e.target;
    const { offsetX: mouseX, offsetY: mouseY } = e;
    //console.table( { parentWidth, parentHeight, parentLeft, parentTop, mouseX, mouseY } );
    console.log(`${roundToTwo((mouseX/parentWidth)*100)}% ${roundToTwo((mouseY/parentHeight)*100)}%`);
}

(function () {
    'use strict';
    console.log('vertexFinder started!');
    document.addEventListener('click', vertexFinder );
})();