我们必须确保带有name属性的type= file应该是相同的 作为upload.single('attr')中传递的参数名

var multer  = require('multer');
var upload = multer({ dest: 'upload/'});
var fs = require('fs');

/** Permissible loading a single file, 
    the value of the attribute "name" in the form of "recfile". **/
var type = upload.single('recfile');

app.post('/upload', type, function (req,res) {

  /** When using the "single"
      data come in "req.file" regardless of the attribute "name". **/
  var tmp_path = req.file.path;

  /** The original name of the uploaded file
      stored in the variable "originalname". **/
  var target_path = 'uploads/' + req.file.originalname;

  /** A better way to copy the uploaded file. **/
  var src = fs.createReadStream(tmp_path);
  var dest = fs.createWriteStream(target_path);
  src.pipe(dest);
  src.on('end', function() { res.render('complete'); });
  src.on('error', function(err) { res.render('error'); });

});

我们必须确保带有name属性的type= file应该是相同的 作为upload.single('attr')中传递的参数名

var multer  = require('multer');
var upload = multer({ dest: 'upload/'});
var fs = require('fs');

/** Permissible loading a single file, 
    the value of the attribute "name" in the form of "recfile". **/
var type = upload.single('recfile');

app.post('/upload', type, function (req,res) {

  /** When using the "single"
      data come in "req.file" regardless of the attribute "name". **/
  var tmp_path = req.file.path;

  /** The original name of the uploaded file
      stored in the variable "originalname". **/
  var target_path = 'uploads/' + req.file.originalname;

  /** A better way to copy the uploaded file. **/
  var src = fs.createReadStream(tmp_path);
  var dest = fs.createWriteStream(target_path);
  src.pipe(dest);
  src.on('end', function() { res.render('complete'); });
  src.on('error', function(err) { res.render('error'); });

});

不同的文件名发布为“recfile”在<input type=“文件”名称=“recfile”占位符=“选择文件”/>和接收为“文件”在upload.single('file')

解决方案:确保发送和接收的文件是相似的upload.single('recfile')

在我的场景中，发生这种情况是因为我重命名了swagger中的一个参数。Yaml，但没有重新加载文档页面。 因此，我尝试使用一个意想不到的输入参数的API。 长话短说，F5是我的朋友。

2022 - 2023的答案

当使用FormData和数组时，multer变量名也必须包含'[]'，这在过去不是这样的。

旧的代码:

const multerConfig = upload.fields([
    {name: 'photos', maxCount: 20}
])

2022年+代码:

const multerConfig = upload.fields([
    {name: 'photos[]', maxCount: 20}
])

这是你可以使用的Api

 const express        = require('express');
 const bodyParser     = require('body-parser');
 const app = express();
 var multer = require('multer');
 const port = 8000;
 app.use(bodyParser.json());
 app.use(bodyParser.urlencoded({ extended: true }));

 app.listen(port, ()=>{
 console.log('We are live on' + port);
 });

 var upload = multer({dest:'./upload/'});

 app.post('/post', upload.single('file'), function(req, res) {
  console.log(req.file);
 res.send("file saved on server");
 });

这也适用于邮差 但是文件没有后缀名为。jpg 任何建议吗? 如下所述

如果上传没有扩展名的文件，这是multer的默认特性，但是，它为您提供了文件对象，您可以使用它更新文件的扩展名。

var filename = req.file.filename; 
var mimetype = req.file.mimetype; 
mimetype = mimetype.split("/"); 
var filetype = mimetype[1]; 
var old_file = configUploading.settings.rootPathTmp+filename; 
var new_file = configUploading.settings.rootPathTmp+filename+'.'+filetype; 
rname(old_file,new_file);