files/en-us/web/api/svgmaskelement/y/index.md
{{APIRef("SVG")}}
The read-only y property of the {{domxref("SVGMaskElement")}} interface returns an {{domxref("SVGAnimatedLength")}} object containing the value of the {{SVGattr("y")}} attribute of the {{SVGElement("mask")}}. It represents the y-axis coordinate of the top-left corner of the masking area.
[!NOTE] Although this property is read-only, it is merely a container for two values you can modify, {{domxref("SVGAnimatedLength.baseVal", "baseVal")}} and {{domxref("SVGAnimatedLength.animVal", "animVal")}}.
An {{domxref("SVGAnimatedLength")}} object. The baseVal property of this object returns an {{domxref("SVGLength")}}, the value of which returns the y value.
html,
body,
svg {
height: 100%;
}
<div>
<svg viewBox="-10 -10 120 120" width="100" height="100">
<mask id="mask" x="0" maskUnits="userSpaceOnUse">
<!-- Everything under a white pixel will be visible -->
<rect x="0" y="0" width="100" height="100" fill="white" />
<!-- Everything under a black pixel will be invisible -->
<path
d="M10,35 A20,20,0,0,1,50,35 A20,20,0,0,1,90,35 Q90,65,50,95 Q10,65,10,35 Z"
fill="black" />
<animate
attributeName="y"
values="0;80;0"
dur="5s"
repeatCount="indefinite" />
</mask>
<polygon points="-10,110 110,110 110,-10" fill="orange" />
<!-- with this mask applied, we "punch" a heart shape hole into the circle -->
<circle cx="50" cy="50" r="50" mask="url(#mask)" />
</svg>
</div>
<pre id="log"></pre>
const mask = document.getElementById("mask");
function displayLog() {
const animValue = mask.y.animVal.value;
const baseValue = mask.y.baseVal.value;
log.textContent = `The 'y.animVal' is ${animValue}.\n`;
log.textContent += `The 'y.baseVal' is ${baseValue}.`;
requestAnimationFrame(displayLog);
}
displayLog();
{{EmbedLiveSample('Example', 100, 160)}}
{{Specifications}}
{{Compat}}