Express implements front-end and back-end communication to upload pictures to the storage database (mysql) fool-proof tutorial (1)_javascript skills

I have been struggling in the front-end pit for more than a year, and I finally made up my mind to write my first blog (although the content is mostly original, it is an integrated content). The reason I started using Express is because I wanted to The test receives and returns images uploaded by the front end to realize image upload. Everyone on the back end is quite busy, so I have no choice but to do it myself (hey, they were all forced out).

This tutorial is suitable for web front-end development who have not been exposed to node and can quickly build their own framework, based on express4.x.

First install express, http://www.expressjs.com.cn/starter/installing.html, and press Enter until the end during the installation process.

After the installation is complete, continue to install the express application skeleton and generate the default project

$ npm install express-generator -g 

(-g means global installation, you can use it directly next time without installing again)

Then run express directly in the myapp folder, and the project directory will be generated directly

Then install all dependent packages:

$ npm install 

Launch this app (MacOS or Linux):

$ DEBUG=myapp npm start 

Use the following command on Windows platform:

> set DEBUG=myapp & npm start 

When you see this page, you have completed the basic project construction, and you can continue to add your own code. (After arriving at this section, you can modify the folder in the public directory to your favorite format, such as: js, css, it is just a path)

Next, you can add your own pages to the project, but so far I have only found that express can load jade templates and ejs. You don’t have to worry about learning jade all over again. Here http://www.html2jade.org/, you can directly use tools to convert html into jade templates, and you can directly add existing projects to it. How to load jade template in express: http://www.expressjs.com.cn/guide/using-template-engines.html. In fact, the writing method of Jade is really simple. You can basically get started by looking at the API. Click here for the learning address. (jade has been integrated into the project, no need to install it again)

Now everyone opens the core app.js

These lines define express routing. You can briefly understand the role of routing. http://www.expressjs.com.cn/guide/routing.html This is very important. , must be understood, it is not difficult, you should be able to understand it quickly.

For example, if you open the http://localhost:3000/users page now, you can understand the code in user.js at a glance. (A get request occurred when opening this page)

Next, let’s not rush to upload pictures, but first test the post and get requests sent by the front end.

Taking post request as an example, we modify layout.jade to look like below

doctype html
html
 head
 title= title
 link(rel='stylesheet', href='/css/style.css')
 script(type="text/javascript", src="/js/jquery.js")
 script(type="text/javascript", src="/js/index.js")
 body
 block content 

Create a new index.js under public/js and load jquery (just for the abbreviation of ajax). Some people may ask why there is no public path, because Express’s built-in express.static can easily host static files, such as pictures, CSS, JavaScript files, etc. Click here for details. The corresponding content of app.js is app.use(express.static(path.join(__dirname, 'public')));

Only in this way can the file be read.

Let’s start modifying the js code. Just write the most basic ajax request in public/js/index.js. The path to send the request here is "/", which is to send the request to the homepage (routing must be understood, routing You must understand, you must understand routing! )

$(document).ready(function() 
{　
$.post('/',
 {num: '12345678'
},
 function(data) 
{　　
 console.log(data) 
 });
}) 

Then modify
in routes/index.js

var express = require('express');
var router = express.Router();
/* GET home page. */
router.get('/', function(req, res, next) {
 res.render('index', { title: 'Express' });
});
router.post('/', function(req, res) { 
 res.send(req.body.num);
});
module.exports = router; 

　　在此监听首页的post请求，req.body.num表示发送过来的数据，大家可以直接打印下req，看看里面包含了什么内容，加深理解（修改完文件后记得重启express）。

　　这时候在控制台中就可以看到返回的数据了。

　　现在大家已经可以使用node接收前端发送的请求了（是不是灰长开心！！），下面进行我们的重头戏，上传图片。

　　因为是测试接口，公司的项目要兼容低版本浏览器，所有plupload.js就上场了(不是我不想用h5的方法)。官网，下载后如图，就够用了。（记得在layout.jade里面加载）

　　把index.js修改成下面的样子,这是个标准的官网上传事例，不理解的在官网看下api，很好理解（其实看变量名字也都能理解~）

$(document).ready(function() {
 var uploader = new plupload.Uploader({
 runtimes: 'html5,flash,silverlight,html4',
 browse_button: 'pickfiles', // you can pass an id...
 container: document.getElementById('container'), // ... or DOM Element itself
 url: '/',
 flash_swf_url: '../js/Moxie.swf',
 silverlight_xap_url: '../js/Moxie.xap',
 filters: {
 max_file_size: '10mb',
 mime_types: [{
 title: "Image files",
 extensions: "jpg,gif,png"
 }, {
 title: "Zip files",
 extensions: "zip"
 }]
 },
 init: {
 PostInit: function() {
 document.getElementById('filelist').innerHTML = '';
 document.getElementById('uploadfiles').onclick = function() {
 uploader.start();
 return false;
 };
 },
 FilesAdded: function(up, files) {
 plupload.each(files, function(file) {
 document.getElementById('filelist').innerHTML += '<div id="' + file.id + '">' + file.name + ' (' + plupload.formatSize(file.size) + ') <b></b></div>';
 });
 },
 UploadProgress: function(up, file) {
 document.getElementById(file.id).getElementsByTagName('b')[0].innerHTML = '<span>' + file.percent + "%</span>";
 },
 Error: function(up, err) {
 document.getElementById('console').appendChild(document.createTextNode("\nError #" + err.code + ": " + err.message));
 },
 FileUploaded: function(up, file, info) { // Called when file has finished uploading 
 $("body").append($(info.response)) 
 },
 UploadComplete: function(up, file) {
 }
 }
 });
 uploader.init();
}) 

　　index.jade修改成下面的样子，主要是添加上传点击的元素，添加了两个按钮而已（不要嫌弃它确实是比较丑--）

extends layout
block content
 h1= title
 p Welcome to #{title}
 #filelist
 #container
 a#pickfiles select files
 a#uploadfiles upload files 

　　这里我们要用到的外部模块是Felix Geisendörfer开发的node-formidable模块。它对解析上传的文件数据做了很好的抽象。 其实说白了，处理文件上传“就是”处理POST数据 —— 但是，麻烦的是在具体的处理细节，所以，这里采用现成的方案更合适点。　　

　　安装formidable模块。

npm install formidable 

　　修改routes/index.js

var express = require('express');
var router = express.Router();
var fs = require('fs');
var formidable = require("formidable");
/* GET home page. */
router.get('/', function(req, res) {
 res.render('index', {
 title: '孟星魂'
 });
});
router.post('/', function(req, res) {
 var form = new formidable.IncomingForm();
 form.uploadDir = "./public/upload/temp/"; //改变临时目录
 form.parse(req, function(error, fields, files) {
 for (var key in files) {
 var file = files[key];
 var fName = (new Date()).getTime();
 switch (file.type) {
 case "image/jpeg":
 fName = fName + ".jpg";
 break;
 case "image/png":
 fName = fName + ".png";
 break;
 default:
 fName = fName + ".png";
 break;
 }
 console.log(file, file.size);
 var uploadDir = "./public/upload/" + fName;
 fs.rename(file.path, uploadDir, function(err) {
 if (err) {
 res.write(err + "\n");
 res.end();
 }
 //res.write("upload image:<br/>");
 res.write("<img src='/upload/" + fName + "' />");
 res.end();
 })
 }
 });
});

module.exports = router;

 　　此时需要在public下手动新建文件夹upload以及下面的temp文件夹。

 　　先把文件上传到临时文件夹，再通过fs重命名移动到指定的目录即可。

　　fs.rename即重命名，但是fs.rename不能夸磁盘移动文件，所以我们需要指定上传的临时目录要和最终目录在同一磁盘下。

　　res.write就是往前端返回的数据，这里我直接返回一个img标签，并添加上传文件的路径，前端只要把标签append到页面中就ok了。

　　完成前端图片上传功能！！

　　今天进行到这里，明天进行讲解node连接数据库的操作。