SVGSymbolElement：viewBox 属性

<svg xmlns="http://www.w3.org/2000/svg" width="200" height="200">
  <defs>
    <symbol id="exampleSymbol" viewBox="0 0 100 100">
      <circle cx="50" cy="50" r="50" fill="blue" />
    </symbol>
  </defs>
  <use href="#exampleSymbol" x="50" y="50" width="100" height="100" />
</svg>

const symbolElement = document.getElementById("exampleSymbol");

// Access the viewBox property
const viewBox = symbolElement.viewBox.baseVal;

console.log(viewBox.x); // Output: 0
console.log(viewBox.y); // Output: 0
console.log(viewBox.width); // Output: 100
console.log(viewBox.height); // Output: 100