What are the nodejs plug-ins?

Nodejs plug-ins include: "node-xlsx", nodemailer, "node-readbility", connect, "express-session", "basic-auth", bcryptjs, puppeteer, nightmare, etc.

The operating environment of this tutorial: windows7 system, nodejs version 12.19.0, DELL G3 computer.

nodejs plug-in

1. Node-xlsx reads and writes Excel

The import and export of excel are many systems Problems that will arise in NodeJS are no exception. Now, we use NodeJS to read and write Excel files

In NodeJS, we use a third-party to read and write files. The tool node-xlsx module supports both the 2003 Excel (.xls) format and the 2007 Excel format (.xlsx)

Now, let’s take a look at the specific operations of this module

Reading operation of Excel

First, we need to install this module

cnpm install node-xlsx --save

The second step is to import the module and read the Excel file

const xlsx=require('node-xlsx');const DBUtil=require('./utils/DBUtil.js');const fs=require('fs');const path=require('path');function readExcel(path){
  var excel=xlsx.parse(path);
  return excel;}var obj=readExcel(path.join(__dirname,"./files/studentinfo.xls"));console.log(obj[0].data);

The above code has completed the reading operation of the Excel file. At this time, what we read is an object, and the information can be seen in the console

For Excel Write operation

Now, we will demonstrate reading the information from a table in the database and then saving it to the local computer. The code is as follows

const excel=require('node-xlsx');const fs=require('fs');const path=require('path');const DBUtil=require('./utils/DBUtil.js');function writeExcel(){
  var conn=DBUtil.getConn();
  conn.query("select * from studentinfo",[],(err,result)=>{
    if(err){

    }
    else{
      var excelArr=[];
      var headerRow=[];
      for(var i in result[0]){
        headerRow.push(i);
      }
      excelArr.push(headerRow);
      for(var i=0;i<result.length;i++){
        var temp=[];
        for(var j=0;j<headerRow.length;j++){
          temp.push(result[i][headerRow[j]]);
        }
        excelArr.push(temp);
      }
      try {
        var buff=excel.build([{name:&#39;学生信息&#39;,data:excelArr}]);
        fs.writeFileSync(path.join(__dirname,"./files/01.xlsx"),buff);
        console.log("ok");
      } catch (error) {
        console.log(err);
      }
    }
  });
  conn.end();}writeExcel();

Here, we found , writing to excel is a little more troublesome, because here, we need to recombine the results obtained in the database and generate Excel

Thinking: If it is generated in the Express framework, The Excel file is as follows for users to download and save locally?

2. Nodemailer sends emails

nodejs is used in many scenarios for sending emails to users. For example, we often After seeing a user register, a registration information will be sent to the user's registered mailbox. At this time, if we want to complete this function, we need to use a third-party module of nodemailer. The specific steps are as follows:

Install the corresponding module

$ cnpm install nodemailer --asve
$ yarn add nodemailer

Import the module and complete the code

const nodemailer=require('nodemailer');var transport = nodemailer.createTransport({
  service:"qq",
  auth:{
    user:"365055754@qq.com",
    pass:"peshapwpokgvcahe"
  }});var options={
  from:"365055754@qq.com",
  to:"lovesnsfi@live.com",
  subject:"这是一封来自nodemailer发送的邮件信息",
  text:"这是一封来自nodemailer发送的邮件信息"+(new Date()).toLocaleString(),
  html:"<h2>这是一封来自<u>nodemail</u>的测试邮件···</h2>"};transport.sendMail(options,(err,info)=>{
  if(err){
    console.log(err);
  }
  else{
    console.log(info);
  }});

Send the message after success

{ accepted: [ 'lovesnsfi@live.com' ],
  rejected: [],
  envelopeTime: 221,
  messageTime: 830,
  messageSize: 801,
  response: '250 Ok: queued as ',
  envelope: { from: '365055754@qq.com', to: [ 'lovesnsfi@live.com' ] },
  messageId: '<2fbef9f1-1041-fd59-1111-0b987e8d81da@qq.com>' }

At this time, as long as the program can be in this u place After completing our send request, the above information will be returned. If we do not see the above information, we need to check the information returned by the error here

Instructions: Here When configuring the sending server, we can use a third-party server or a built-in server

Thinking: If the sent content is replaced with a template

const fs=require('fs');const path=require('path');class MailTemplateModel{
  constructor(userName,u_id,registerTime,mail){
    this.userName=userName;
    this.u_id=u_id;
    this.registerTime=registerTime;
    this.mail=mail;
  }
  toString(){
    var str=`尊敬的${this.userName}你好！
    欢迎注册成为我们的会员，你的账号为${this.u_id},你的注册时间为：${this.registerTime}。
    请注意保管好您的账号与密码，如有问题欢迎发送邮件至${this.mail}!
    谢谢！祝您生活愉快！`;
    return str;
  }}module.exports=MailTemplateModel;

The above code encapsulates the email content to be sent into an object, and then uses template syntax to splice strings

Thinking: We wrote the above email content in In an external separate txt file, it is then implemented through the replacement of the String object. How to implement this function?

3. child_process

can create a child process and execute a shell script.

4. node-readbility

A plug-in that can convert website content into simple content.

5. connect

In fact, express also uses this plug-in, and you can also write web programs using connect.

6. express-session

This is a plug-in that uses sessions. The default is forever, which is different from tomcat 30 minutes, so you need to set it yourself. overtime time.

7. The basic-auth plug-in

is used for the simplest authentication method and is generally used for API requests.

8. bcryptjs plug-in (an error is always reported during the bcrypt installation process)

is used to perform hash processing using salt.

9. Collection of reptiles:

(1) Crawling of static pages and api data: request cheerio/jsdom, request is a Request library, you can request post and get information. After obtaining the html data, use a third-party parsing library to parse it, cheerio can be used. For js dynamically rendered pages, you can consider using jsdom, but unfortunately, this is synchronous, and it is not browsing after all. device.

(2) Crawling of dynamically rendered pages

puppeteer: Using chromiun browser, asynchronous request, very efficient, and opens up a lot of browser operations api, very convenient.

nightmare: The API is very convenient to use. Use the browser in electron. Although I have not used it before, I feel that this is not as flexible as puppeteer.

jsdom: Synchronization has put me off using it. Same as selenium.

10、moment.js

This is a lightweight format parsing library. If you write the format parsing function yourself, you will need several dozen lines of function code. It is very convenient to use this.

For more node-related knowledge, please visit: nodejs tutorial! !

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