Node.js：Multer上传的承诺？

我有这个快速路由与multerfile upload。 上传完成后，我想将图像编码为base64并发送响应。

但是，当我这样做时，代码尝试执行base64编码之前，文件创build到文件夹。

编辑 ：增加了存储和上传function

const storage = multer.diskStorage({ destination: (req, file, callback) => { if (!fs.existsSync('./uploads')) { fs.mkdirSync('./uploads'); } let path = './uploads'; callback(null, path); }, filename(req, file, cb) { let fileExt = file.originalname.substring(file.originalname.lastIndexOf('.')).toLowerCase(); if (!imageFilter(fileExt)) { return false; } else { cb(null, file.originalname); } }, onError: function (err, next) { console.log('error', err); next(err); }, }); const upload = multer({ storage, limits: { fileSize: 1000 * 1000 * 2 // 2 MB } }).single('file'); router.post('/upload', function (req, res) { var directory = 'uploads'; fs.readdir(directory, (err, files) => { if (err) throw err; for (var file of files) { fs.unlink(path.join(directory, file), err => { if (err) throw err; }); } }); upload(req, res, function (err) { if (err) { return res.status(404).json({ success: false, message: 'File is too large. (Max 2MB)' }); } var file = req.file; var base64str = base64_encode('./uploads/' + file.originalname); return res.status(200).json({ success: true, url: 'http://' + ip.address() + ':' + constants.PORT + '/api/uploads/' + file.originalname, image: 'data:image/png;base64,' + base64str }); }); }); 

什么才是实现正确的操作顺序的最明智的方式。 可能承诺或asynchronous/等待？

Answer 1

这个解决scheme为我工作：

节点v8.4.0是必需的

 //app.js const fs = require('fs'); const express = require('express'); const cors = require('cors'); const bodyParser = require('body-parser'); const app = express(); app.use(cors({credentials: true, origin: 'http://localhost:4200'})); app.use(bodyParser.json()); app.use(bodyParser.urlencoded({ extended: true })); const Uploader = require('./Uploader.js'); const uploader = new Uploader(); app.post('/upload', uploader.startUpload); //Uploader.js const util = require("util"); const crypto = require("crypto"); const multer = require('multer'); class Uploader { constructor() { const storageOptions = multer.diskStorage({ destination: function(req, file, cb) { cb(null, __dirname + '/uploads/') }, filename: function(req, file, cb) { crypto.pseudoRandomBytes(16, function(err, raw) { cb(null, raw.toString('hex') + Date.now() + '.' + file.originalname); }); } }); this.upload = multer({ storage: storageOptions }); } async startUpload(req, res) { let filename; try { const upload = util.promisify(this.upload.any()); await upload(req, res); filename = req.files[0].filename; } catch (e) { //Handle your exception here } return res.json({fileUploaded: filename}); } }