save-svg-as-png.js

//from https://qiita.com/skryoooo/items/a37455bef54321a6195a
//変更内容：関数化とconst化

function saveSvgAsPng(el) {
  const svgData = new XMLSerializer().serializeToString(el);
  const canvas = document.createElement("canvas");
  canvas.width = el.width.baseVal.value;
  canvas.height = el.height.baseVal.value;

  const ctx = canvas.getContext("2d");
  const image = new Image();
  image.onload = function() {
    ctx.drawImage(image, 0, 0);
    const a = document.createElement("a");
    a.href = canvas.toDataURL("image/png");
    a.setAttribute("download", "image.png");
    a.dispatchEvent(new MouseEvent("click"));
  };
  image.src =
    "data:image/svg+xml;charset=utf-8;base64," +
    btoa(unescape(encodeURIComponent(svgData)));
}

function download() {
  const svg = document.querySelector("svg");
  saveSvgAsPng(svg);
}