javascript resize image base64

function resizeImage(base64Str, maxWidth = 400, maxHeight = 350) {
  return new Promise((resolve) => {
    let img = new Image()
    img.src = base64Str
    img.onload = () => {
      let canvas = document.createElement('canvas')
      const MAX_WIDTH = maxWidth
      const MAX_HEIGHT = maxHeight
      let width = img.width
      let height = img.height

      if (width > height) {
        if (width > MAX_WIDTH) {
          height *= MAX_WIDTH / width
          width = MAX_WIDTH
        }
      } else {
        if (height > MAX_HEIGHT) {
          width *= MAX_HEIGHT / height
          height = MAX_HEIGHT
        }
      }
      canvas.width = width
      canvas.height = height
      let ctx = canvas.getContext('2d')
      ctx.drawImage(img, 0, 0, width, height)
      resolve(canvas.toDataURL())
    }
  })
}