js计算图片大小（promise）

const calculateSize = (imageUrl) => {
  return new Promise((resolve, reject) => {
    const img = new Image()
    img.onload = () =>
      resolve({
         img.width,
        height: img.height,
      })
    img.onerror = reject
    img.src = imageUrl
  })
}

// 使用
const getSize = await calculateSize(imageUrl)
console.log(getSize); // { 200, height: 200}