Express and multer implement the image upload function in node

In the front end, we use ajax to asynchronously upload images, use file-input to upload images, use formdata objects to process image data, post to the server, and use multer middleware in node to process the upload routing interface. . This article mainly introduces the use of express+multer to implement the image upload function in node. Friends who need it can refer to it. I hope it can help everyone.

multer document

package.json

html part

<p>
    <label>File input:</label>
    <input>
    </p><p></p>
    <img  src="/static/imghwm/default1.png" data-src="https://cdn.bootcss.com/jquery/3.3.1/jquery.min.js" class="lazy" alt="Express and multer implement the image upload function in node" >
  
  <button>提交</button>
  

js part

<script></script>
  <script>
    //上传图片的业务逻辑函数
    function uploadFile(){
      //上传图片的input
      var file = document.getElementById("file")
      //因为准备用post提交，又因为图片的内容比较大，所以我们选择使用formdata来承载数据
      //创建formdata对象
      var formData = new FormData();
      //给formdata对象中放入数据(键值对的方式)
      formData.append(&#39;file&#39;,file.files[0]);
      //提交请求
      $.ajax({
        url: &#39;/upload&#39;,//请求路径
        type: &#39;POST&#39;,
        data: formData,
        contentType: false,//为了让浏览器根据传入的formdata来判断contentType
        processData: false,//同上
        success: function(data){
          if(200 === data.code) {
            $(&#39;#result&#39;).html("上传成功！");
            $(&#39;#img&#39;).attr(&#39;src&#39;,data.data);
          } else {
            $(&#39;#result&#39;).html("上传失败！");
          }
          console.log(2)
        },
        error: function(){
          $("#result").html("与服务器通信发生错误");
        }
      });
      console.log(1)
    }
    //给按钮添加点击事件
    function postPage() {
        //上传按钮
        var uploada = document.getElementById(&#39;upload&#39;);
        uploada.addEventListener("click",function () {
          uploadFile();
        },false);
    }
    window.onload = function () {
      postPage();
    }
</script>

NodeJS logic code

const http = require('http')
const path = require('path')
const express = require('express')
//是nodejs中处理multipart/form-data数据格式(主要用在上传功能中)的中间件
//文档：https://github.com/expressjs/multer/blob/master/doc/README-zh-cn.md
const multer = require('multer')
const app = express()
//配置express的静态目录
app.use(express.static(path.join(__dirname, 'public')));
app.get('/',(req,res)=>{
  res.sendFile(__dirname+'/index.html')
})
//配置diskStorage来控制文件存储的位置以及文件名字等
var storage = multer.diskStorage({
  //确定图片存储的位置
  destination: function (req, file, cb){
    cb(null, './public/uploadImgs')
  },
![](http://images2017.cnblogs.com/blog/1283058/201802/1283058-20180201154342296-515041615.png)
  //确定图片存储时的名字,注意，如果使用原名，可能会造成再次上传同一张图片的时候的冲突
  filename: function (req, file, cb){
    cb(null, Date.now()+file.originalname)
  }
});
//生成的专门处理上传的一个工具，可以传入storage、limits等配置
var upload = multer({storage: storage});
//接收上传图片请求的接口
app.post('/upload', upload.single('file'), function (req, res, next) {
  //图片已经被放入到服务器里,且req也已经被upload中间件给处理好了（加上了file等信息）
  //线上的也就是服务器中的图片的绝对地址
  var url = '/uploadImgs/' + req.file.filename
  res.json({
    code : 200,
    data : url
  })
});
http.createServer(app).listen(3000,()=>{
  console.log('server is listening')
})

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