文件上传但 multer 代码未执行 |节点 + multer + express + formdata

Question

我正在使用form，multer，express和nodejs将视频文件上传到本地文件夹。

视频文件上传到本地文件夹 - 每次我通过表单上传时。但是，upload中的代码只是偶尔执行。5次一次。即app.post内的console.log('33');并不总是被打印出来。但是，console.log('1')(post内部和upload之前(每次都有效。

server.js代码

var Express = require('express');
var multer = require('multer');
var mkdirp = require('mkdirp');
var app = Express();
var cors = require('cors');    
app.use(cors());

var Storage = multer.diskStorage({
destination: function(req, file, cb) {
var dir = './client/public/video/';
mkdirp(dir, function(err) {
if(err) {
console.error(err);
}
cb(null, dir);
});
console.log("Upload: saved to " + dir + file.originalname);
},
filename: function(req, file, callback) {
callback(null, file.fieldname + "_" + Date.now() + "_" + file.originalname);
}
});
var upload = multer({
storage: Storage
}).single("file");

app.post("/api", function(req, res) {
console.log('1');
upload(req, res, function(err) {
console.log('33');
if (err) {
return res.end("Something went wrong!");
}
return res.status(200).end("File uploaded successfully!.");
});
});
var server = app.listen(9000, function () {
console.log('app listening at 9000');
});

app.js代码

import React, { Component } from "react";
import axios from "axios";
class App extends Component {
state = {
file: null
};
handleOnChange = e => this.setState({ [e.target.name]: e.target.value });
handleOnUploadFile = e => this.setState({ file: e.target.files[0] });
handleOnSubmit = e => {
e.preventDefault();
const formData = new FormData();
formData.append("file", this.state.file);

axios
.post("http://localhost:9000/api", formData, {
headers: {
'accept': 'video/mp4',
'Accept-Language': `en-US,en;q=0.8`,
'Content-Type': `multipart/form-data; boundary=${formData._boundary}`,
}  
})
.then(res => console.log(res.data))
.catch(err => console.error(err));
};
render() {
return (
<form>
<input type="file" encType="multipart/form-data"
name="file"
accept="video/mp4"
onChange={this.handleOnUploadFile}/>

<button type="submit" className="btn btn-danger" onClick={this.handleOnSubmit}>
Submit
</button>
</form>
);
}
}
export default App;

我是反应/节点 js 的新手。尝试了很多其他帖子的建议，但找不到解决方案。

Answer 1

尝试添加async和await。

server.js

var Express = require('express');
var multer = require('multer');
var mkdirp = require('mkdirp');
var app = Express();
var cors = require('cors');    
app.use(cors());

var Storage = multer.diskStorage({
destination: function(req, file, cb) {
var dir = './client/public/video/';
mkdirp(dir, function(err) {
if(err) {
console.error(err);
}
cb(null, dir);
});
console.log("Upload: saved to " + dir + file.originalname);
},
filename: function(req, file, callback) {
callback(null, file.fieldname + "_" + Date.now() + "_" + file.originalname);
}
});
var upload = multer({
storage: Storage
}).single("file");

app.post("/api", function(req, res) {
console.log('1');
upload(req, res, function(err) {
console.log('33');
if (err) {
return res.end("Something went wrong!");
}
return res.status(200).end("File uploaded successfully!.");
});
});
app.get("/", function(req, res) {
console.log('1');
return res.status(200).json({});
});
var server = app.listen(9900, function () {
console.log('app listening at 9900');
});

App.js

import React, { Component } from "react";
import axios from "axios";
class App extends Component {
state = {
file: null
};
handleOnChange = e => this.setState({ [e.target.name]: e.target.value });
handleOnUploadFile = e => this.setState({ file: e.target.files[0] });
handleOnSubmit = async e => {
e.preventDefault();
const formData = new FormData();
formData.append("file", this.state.file);

await axios
.post("http://localhost:9900/api", formData, {
headers: {
'accept': 'video/mp4',
'Accept-Language': `en-US,en;q=0.8`,
'Content-Type': `multipart/form-data; boundary=${formData._boundary}`,
}  
})
.then(res => console.log(res.data))
.catch(err => console.error(err));
};
render() {
return (
<>
<h1>{"<b>hello</b>".bold()}</h1>
<form>
<input type="file" encType="multipart/form-data"
name="file"
accept="video/mp4"
onChange={this.handleOnUploadFile}/>

<button type="submit" className="btn btn-danger" onClick={this.handleOnSubmit}>
Submit
</button>
</form>
</>
);
}
}
export default App;

Answer 2

尝试为您的上传函数使用 promise：

var Express = require('express');
var multer = require('multer');
var mkdirp = require('mkdirp');
var app = Express();
var cors = require('cors');    
app.use(cors());

var Storage = multer.diskStorage({
destination: function(req, file, cb) {
var dir = './client/public/video/';
mkdirp(dir, function(err) {
if(err) {
console.error(err);
}
cb(null, dir);
});
console.log("Upload: saved to " + dir + file.originalname);
},
filename: function(req, file, callback) {
callback(null, file.fieldname + "_" + Date.now() + "_" + file.originalname);
}
});
var upload = multer({
storage: Storage
}).single("file");

app.post("/api", function(req, res) {
console.log('1');

upload(req, res).then((file, err) => {
console.log('33');
if (err) {
return res.end("Something went wrong!");
}
return res.status(200).end("File uploaded successfully!.");
})

});
var server = app.listen(9000, function () {
console.log('app listening at 9000');
});

另一个想法是将上传本身包装在一个承诺中：

var Storage = multer.diskStorage({
return new Promise((resolve, reject) => {
destination: function(req, file, cb) {
var dir = './client/public/video/';
mkdirp(dir, function(err) {
if(err) {
reject(err)
}
cb(null, dir);
});
console.log("Upload: saved to " + dir + file.originalname);
},
filename: function(req, file, callback) {
resolve(callback(null, file.fieldname + "_" + Date.now() + "_" + file.originalname);)
}
})
});