typescript: get image rect size

getImageSize.ts

/**
 * srcから縦横幅を取得する
 *
 * @export
 * @param {string} src
 * @returns {Promise<{ width: number; height: number }>}
 */
export default async function getImageSize(
  src: string
): Promise<{ width: number; height: number }> {
  return new Promise((resolve, reject) => {
    const image = new window.Image();

    const onload = () => {
      resolve({
        width: image.naturalWidth,
        height: image.naturalHeight,
      });
    };

    const onerror = () => {
      reject();
    };

    image.onload = onload;
    image.onerror = onerror;
    image.src = src;
  });
}