How TO - Scroll Drawing
Learn how to draw on scroll using JS and SVG.
Scroll Drawing
Using SVG and JavaScript to draw a triangle on scroll - note that it has to be a <path> element:
Example
<svg id="mySVG">
<path fill="none" stroke="red" stroke-width="3"
id="triangle" d="M150 0 L75 200 L225 200 Z"/>
</svg>
<script>
// Get the id of the
<path> element and the length of <path>
var triangle =
document.getElementById("triangle");
var length = triangle.getTotalLength();
// The start position of the drawing
triangle.style.strokeDasharray =
length;
// Hide the triangle by offsetting dash. Remove this line to
show the triangle before scroll draw
triangle.style.strokeDashoffset =
length;
// Find scroll percentage on scroll (using cross-browser
properties), and offset dash same amount as percentage scrolled
window.addEventListener("scroll", myFunction);
function myFunction()
{
var scrollpercent = (document.body.scrollTop +
document.documentElement.scrollTop) / (document.documentElement.scrollHeight
- document.documentElement.clientHeight);
var draw = length *
scrollpercent;
// Reverse the drawing (when scrolling upwards)
triangle.style.strokeDashoffset = length - draw;
}
</script>
Try it Yourself »
