我想通了要将文件/图像上传到 multer 我们需要一个表单 enctype="multipart/form-data" 没有它不能与 multer 一起使用

我从子组件获取文件，然后 1）我创建了一个空表单，其中 encType="mutipart/form-data" 2) 当我收到文件时，我创建了一个新的 FormData（带有对 myform 的引用）3）然后附加formData 中的键和值 4) 创建 fetch.post() 并且它可以工作:)

参考提交代码

React 父组件 Upload.js

import React, { Component } from 'react'

import { ImageWithoutForm } from "../app/components/ImageUpload";


export default class UploadFile extends Component {
    onImageLoad(e){
        console.log('onImageLoad', e.target.files[0]);
        this.uploadForm(e.target.files[0]);
    }

    uploadForm(file){
        let form = new FormData(this.refs.myForm);
        form.append('myImage', file);
        fetch('/upload-image', {
          method: 'POST',
          body: form
        }).then(res => console.log('res of fetch', res));
    }

  render() {
    return (
      <div>
        <h4>Upload Image</h4>
        <ImageWithoutForm onImageLoad={(e)=>this.onImageLoad(e)} />
        <form id="upload_form" ref="myForm"  encType="multipart/form-data">
        </form>
      </div>
    )
  }
}

使用输入响应子组件以加载文件 ImageWithoutForm.js

import React, { Component } from 'react'

export  class ImageWithoutForm extends Component {

    handleSubmit(e){
        this.props.onImageLoad(e);
    }


  render() {
    return (
      <div>
            <input type="file" onChange={(e)=>this.handleSubmit(e)}/>
      </div>
    )
  }
}

从某人的 github 存储库中获取的 Express Route 文件和自定义的 UploadImage.js

const express = require('express');
const multer = require('multer');
const path = require('path');

// Set Storage Engine
const storage = multer.diskStorage({
  destination: './public/uploads/',
  filename: function(req, file, cb){
    cb(null,file.fieldname + '-' + Date.now() + path.extname(file.originalname));
  }
});

// Init Upload
const upload = multer({
  storage: storage,
  limits:{fileSize: 1000000},
  fileFilter: function(req, file, cb){
    checkFileType(file, cb);
  }
}).single('myImage');

// Check File Type
function checkFileType(file, cb){
  // Allowed ext
  const filetypes = /jpeg|jpg|png|gif/;
  // Check ext
  const extname = filetypes.test(path.extname(file.originalname).toLowerCase());
  // Check mime
  const mimetype = filetypes.test(file.mimetype);

  if(mimetype && extname){
    return cb(null,true);
  } else {
    cb('Error: Images Only!');
  }
}

// Init app
const app = express.Router();


// Public Folder
app.use(express.static('./public'));


app.post('/', (req, res) => {
    console.log('handling upload image');
  upload(req, res, (err) => {
    if(err){
      console.log('first err', err);
      res.send({
        msg: err
      });
    } else {
      if(req.file == undefined){
        console.log('Error: No File Selected!')
        res.send({
          msg: 'Error: No File Selected!'
        });
      } else {
        console.log('File Uploaded!')
        res.send({
          msg: 'File Uploaded!',
          file: `uploads/${req.file.filename}`
        });
      }
    }
  });
});

module.exports = app;

在我的快递 app.js 中只需要路由文件 ImageUpload.js

并映射到这样的路线

var uploadImage = require('./routes/UploadImage');
server.use('/upload-image', uploadImage);