<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <title>doc</title> <style> body { height: 5000px; background: -webkit-linear-gradient(top, orange, darkblue); background: linear-gradient(to bottom, orange, darkblue); } h1 { font-family: "HelveticaNeue-Light", "Helvetica Neue Light", "Helvetica Neue", Helvetica, Arial, "Lucida Grande", sans-serif; font-weight: 300; color: white; text-transform: uppercase; text-align: center; font-size: 22px; letter-spacing: 5px; font-weight: 100; padding: 25px 15px; text-shadow: 1px 1px 1px #333; } #star-svg { position: fixed; top: 50%; left: 50%; width: 150px; height: 150px; margin: -75px 0 0 -75px; } </style> </head> <body> <h1>Scroll-to-draw</h1> <svg xmlns="https://www.w3.org/2000/svg" viewBox="0 0 100.6 107.6" id="star-svg"> <path fill="none" stroke="white" stroke-width="2" id="star-path" d="M43.7,65.8L19.9,83.3c-2.9,1.9-5.1,3.2-7.9,3.2c-5.7,0-10.5-5.1-10.5-10.8 c0-4.8,3.8-8.2,7.3-9.8l27.9-12L8.8,41.4c-3.8-1.6-7.3-5.1-7.3-9.8c0-5.7,5.1-10.5,10.8-10.5c2.9,0,4.8,1,7.6,3.2l23.8,17.4 l-3.2-28.2c-1-6.7,3.5-12,9.8-12c6.3,0,10.8,5.1,9.8,11.7L57,41.8l23.8-17.4c2.9-2.2,5.1-3.2,7.9-3.2c5.7,0,10.5,4.8,10.5,10.5 c0,5.1-3.5,8.2-7.3,9.8L63.9,53.8l27.9,12c3.8,1.6,7.3,5.1,7.3,10.1c0,5.7-5.1,10.5-10.8,10.5c-2.5,0-4.8-1.3-7.6-3.2L57,65.8 l3.2,28.2c1,6.7-3.5,12-9.8,12c-6.3,0-10.8-5.1-9.8-11.7L43.7,65.8z" /> </svg> <script> // Get a reference to the <path> var path = document.querySelector('#star-path'); // Get length of path... ~577px in this case var pathLength = path.getTotalLength(); // Make very long dashes (the length of the path itself) path.style.strokeDasharray = pathLength + ' ' + pathLength; // Offset the dashes so the it appears hidden entirely path.style.strokeDashoffset = pathLength; // Jake Archibald says so // https://jakearchibald.com/2013/animated-line-drawing-svg/ path.getBoundingClientRect(); // When the page scrolls... window.addEventListener("scroll", function(e) { // What % down is it? // https://stackoverflow.com/questions/2387136/cross-browser-method-to-determine-vertical-scroll-percentage-in-javascript/2387222#2387222 // Had to try three or four differnet methods here. Kind of a cross-browser nightmare. var scrollPercentage = (document.documentElement.scrollTop + document.body.scrollTop) / (document.documentElement.scrollHeight - document.documentElement.clientHeight); // Length to offset the dashes var drawLength = pathLength * scrollPercentage; // Draw in reverse path.style.strokeDashoffset = pathLength - drawLength; // When complete, remove the dash array, otherwise shape isn't quite sharp // Accounts for fuzzy math if (scrollPercentage >= 0.99) { path.style.strokeDasharray = "none"; } else { path.style.strokeDasharray = pathLength + ' ' + pathLength; } }); </script> </body> </html> </html>