<b-form-file placeholder="上传封面图(建议尺寸：400*300像素)" 
              browse-text="文件" v-model="file" 
              class="title" accept=".jpg, .jpeg, .png, .webp, .gif" >
</b-form-file>

function upImage(file){
  return new Promise(resolve => {
    const reader = new FileReader()
    reader.readAsArrayBuffer(file)
    reader.onload = (event) => {
      this.ipfs.add({
            path: file.name,
            content: Buffer.from(event.target.result)
          },
          (error, added) => {
            if (error) {
              console.log(123, error)
            } else {
              //上传成功
              console.log(234, added[0].hash)
              resolve(added[0].hash)
            }
          })
    }
  })
}