连续保存文件出错，文件内容不全

用如下代码保存文件，中间会有数据丢失，请赐教，不甚感激。

async function addFileString () {
const readFile = await fileHandle.value.getFile()
readFile.text().then((result) => {
blob1.value = new Blob([result])
})

  const writableStream = await fileHandle.value.createWritable()

  const blob = new Blob(['Hello, world!'])
  await writableStream.write(blob1.value)
  await writableStream.write(blob)

  await writableStream.close()
}