Multer文件上传错误（nodejs和react）

Question

我已经从客户那里发送了这个请求。

if(file){
      const data = new FormData()
      const fileName = Date.now() + file.name
      data.append('file', file) // file comes from state while submitting
      data.append('name', fileName)
      try {
        await axios.post('/upload_image', data)      
      } catch (error) {
        console.log(error.message);
      }
}

节点

const multer = require('multer')


// file upload
const storage = multer.diskStorage({
  destination: (req, file, cb) => {
    console.log(req.body);
    cb(null, "./public/images/");
  },
  filename: (req, file, cb) => {
    cb(null, req.body.name)
  },
});
const upload = multer({ storage });
router.post("/upload_image", upload.single('file'), (req,res)=>{
  console.log(req.body);
    try {
        res.status(200).json("file uploaded successfully")
    } catch (error) {
        console.log(error.message);
    }
});

如果我在

中打印req.body

router.post("/upload_image", upload.single('file'), (req,res)=>{
 console.log(req.body.name)
console.log(req.file)
......................
.......................
})

此处打印名称，req.file 也打印。但是，里面

const storage = multer.diskStorage({
  destination: (req, file, cb) => {
    ...................
..............................
  },
  filename: (req, file, cb) => {
    console.log(req.body.name); //undefined  
    cb(null, req.body.name)
  },
});

名称变为未定义且应用程序崩溃。为什么 req 对象没有转到 diskStorage 函数。这里有什么问题？

Answer 1

来自multer documentation：

Note that req.body might not have been fully populated yet. It depends on the order that the client transmits fields and files to the server.

如果您在前端的文件前附加名称，该名称应该在req.body.name.

处可用

// Append name first before we send the file
// so we can access it in the backend
data.append('name', fileName);
data.append('file', file);

或者，您可以将文件名作为第三个参数直接发送到追加函数：

data.append('file', file, fileName);

然后您可以使用 req.file.originalname 在后端访问文件名。每当您在 Node.js.

中处理文件上传时，请参阅此免费 Request Parsing in Node.js Guide