node简单实现一个更改头像功能的示例

<img class="nav-user-photo" src="<%= user.picture.replace(/public(\/.*)/, "$1") %>" alt="Photo" style="height: 40px;"/>
<form enctype="multipart/form-data" method="post" name="fileInfo">
  <input type="file" accept="image/png,image/jpg" id="picUpload" name="file">
</form>
<button type="button" class="btn btn-primary" id="modifyPicV">确定</button>

document.querySelector('#modifyPicV').addEventListener('click', function () {
  let formData = new FormData();
  formData.append("file",$("input[name='file']")[0].files[0]);//把文件对象插到formData对象上
  console.log(formData.get('file'));
  $.ajax({
    url:'/modifyPic',
    type:'post',
    data: formData,
    processData: false, // 不处理数据
    contentType: false,  // 不设置内容类型
    success:function () {
      alert('success');
      location.reload();
    },
  })
});

let express = require('express');
let router = express.Router();
let fs = require('fs');
let {User} = require('../data/db');
let formidable = require('formidable');
let cacheFolder = 'public/images/';//放置路径
router.post('/modifyPic', function (req, res, next) {
  let userDirPath = cacheFolder + "Img";
  if (!fs.existsSync(userDirPath)) {
    fs.mkdirSync(userDirPath);//创建目录
  }
  let form = new formidable.IncomingForm(); //创建上传表单
  form.encoding = 'utf-8'; //设置编码
  form.uploadDir = userDirPath; //设置上传目录
  form.keepExtensions = true; //保留后缀
  form.maxFieldsSize = 2 * 1024 * 1024; //文件大小
  form.type = true;
  form.parse(req, function (err, fields, files) {
    if (err) {
      return res.json(err);
    }
    let extName = ''; //后缀名
    switch (files.file.type) {
      case 'image/pjpeg':
        extName = 'jpg';
        break;
      case 'image/jpeg':
        extName = 'jpg';
        break;
      case 'image/png':
        extName = 'png';
        break;
      case 'image/x-png':
        extName = 'png';
        break;
    }
    if (extName.length === 0) {
      return res.json({
        msg: '只支持png和jpg格式图片'
      });
    } else {
      let avatarName = '/' + Date.now() + '.' + extName;
      let newPath = form.uploadDir + avatarName;
      fs.renameSync(files.file.path, newPath); //重命名
      console.log(newPath)
      //更新表
      User.update({
        picture: newPath
      }, {
        where: {
          username: req.session.user.username
        }
      }).then(function (data) {
        if (data[0] !== undefined) {
          User.findAll({
            where: {
              username: req.session.user.username
            }
          }).then(function (data) {
            if (data[0] !== undefined) {
              req.session.user.picture = data[0].dataValues.picture;
              res.send(true);
            } else {
              res.send(false);
            }
          })
        }
      }).catch(function (err) {
        console.log(err);
      });
    }
  });
});