restart

<svg viewBox="0 0 220 200" xmlns="http://www.w3.org/2000/svg">
  <rect y="30" width="100" height="100">
    <animate attributeType="XML" attributeName="y" from="30" to="100"
        dur="5s" repeatCount="1" restart="always" />
  </rect>
  <rect x="120" y="30" width="100" height="100">
    <animate attributeType="XML" attributeName="y" from="30" to="100"
        dur="5s" repeatCount="1" restart="whenNotActive"/>
  </rect>
  <a id="restart"><text y="20">Restart animation</text></a>
</svg>

document.getElementById("restart").addEventListener("click", evt => {
  document.querySelectorAll("animate").forEach(element => {
    element.beginElement();
  });
});