How to implement file upload in nodejs+express

This article mainly introduces the use of nodejs express to complete simple file upload functions. Friends who need it can refer to it

1. Create an express project

express -e nodejs-uploadfile

2. Download multer middleware

npm i multer or yarn multer

3. Reference multer in routes/index.js. Since file operations are also used, you must also reference the fs module and specify the file. Upload directory

const multer = require('multer');
const fs = require('fs');
const UPLOAD_PATH = './uploads'

Single file upload: The files in index.html are as follows (the type of the form file must be enctype="multipart/form-data"),

<form action="/upload" method="post" enctype="multipart/form-data">
 <input name="fileUpload" type="file" />
 <img src="/static/imghwm/default1.png"  data-src="" alt="  class="lazy"   alt="">
 <button type="submit">上传</button>
</form>

in routes/ Add the upload route to index.js to handle the operation of uploading files

router.post('/upload', upload.single('fileUpload'), function (req, res, next) {
 const { file } = req;
 fs.readFile(file.path, function(err, data) {
 fs.writeFile(`${UPLOAD_PATH}/${file.originalname}`, data, function (err) {
  if (err) res.json({ err })
  res.json({
  msg: '上传成功'
  });
 });
 })
})

If the uploaded file is an image, you can also use the FileReader object to preview the image

(function($){
 $('input').on('change', function(event) {
 var files = event.target.files,
  reader = new FileReader();
 if(files && files[0]){
  reader.onload = function (ev) {
   $('img').attr('src', ev.target.result);
  }
  reader.readAsDataURL(files[0]);
 }
 })
}(jQuery))

Multiple file upload: Multiple files The principle of uploading is the same as that of single file upload. The code is as follows:

router.post('/upload', upload.array('fileUpload'), function (req, res, next) {
 const files = req.files;
 const response = [];
 const result = new Promise((resolve, reject) => {
 files.map((v) => {
  fs.readFile(v.path, function(err, data) {
  fs.writeFile(`${UPLOAD_PATH}/${v.originalname}`, data, function(err, data) {
   const result = {
   file: v,
   }
   if (err) reject(err);
   resolve('成功');
  })
  })
 })
 })
 result.then(r => {
 res.json({
  msg: '上传成功',
 })
 }).catch(err => {
 res.json({ err })
 });
})

The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.

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