files/en-us/web/api/svgmarkerelement/viewbox/index.md
{{APIRef("SVG")}}
The viewBox read-only property of the {{domxref("SVGMarkerElement")}} interface returns an {{domxref("SVGAnimatedRect")}} object which contains the values set by the {{SVGattr("viewBox")}} attribute on the {{SVGElement("marker")}}.
An {{domxref("SVGAnimatedRect")}} object. The baseVal property of this object returns an {{domxref("SVGRect")}} object, from which can be returned the x and y co-ordinates, plus the width and height of the {{SVGElement("marker")}} {{SVGattr("viewBox")}} attribute.
This example demonstrates how to return the value of the width set for the {{SVGattr("viewBox")}} attribute of {{SVGElement("marker")}}.
<svg id="svg" viewBox="0 0 100 100" xmlns="http://www.w3.org/2000/svg">
<defs>
<marker
id="arrow"
viewBox="0 0 10 10"
refX="5"
refY="5"
preserveAspectRatio="xMidYMid meet"
markerWidth="6"
markerHeight="6"
orient="auto-start-reverse">
<path d="M 0 0 L 10 5 L 0 10 z" />
</marker>
</defs>
</svg>
const marker = document.getElementById("arrow");
console.log(marker.viewBox.baseVal.width); // 10
{{Specifications}}
{{Compat}}