Node.js makes a simple crawler case tutorial

var http = require('http');
var fs = require('fs');
var cheerio = require('cheerio');
var request = require('request');
var i = 0;
//Initial url 
var url = "http://cs.whu.edu.cn/a/xinwendongtaifabu/2018/0428/7053.html"; 

function fetchPage(x) { //Encapsulates a layer of function startRequest(x); 
}

function startRequest(x) {
     //Use http module to initiate a get request to the server http.get(x, function (res) {     
        var html = ''; //Used to store the entire HTML content of the requested web page var titles = [];    
        res.setEncoding('utf-8'); //Prevent Chinese garbled characters //Listen to data events and take a piece of data at a time res.on('data', function (chunk) {   
	      html += chunk;
	 });
     //Listen for the end event. If the HTML of the entire webpage content is obtained, execute the callback function res.on('end', function () {
         var $ = cheerio.load(html); //Use cheerio module to parse html
         var news_item = {
          //Get the title of the article title: $('div#container dt').text().trim(),
          i: i = i + 1,     
       };

	  console.log(news_item); //Print news information var news_title = $('div#container dt').text().trim();
	  savedContent($,news_title); //Store the content and title of each article savedImg($,news_title); //Store the image and title of each article //URL of the next article
       var nextLink="http://cs.whu.edu.cn" + $("dd.Paging a").attr('href');
       str1 = nextLink.split('-'); //Remove the Chinese characters after the url str = encodeURI(str1[0]);  
       //This is one of the highlights. By controlling I, you can control how many articles to crawl. Wuhan University has only 8 articles, so it is set to 8
       if (i <= 8) {                
          fetchPage(str);
       }
	});
}).on('error', function (err) {
      console.log(err);
    });
 }
//The function is to store the crawled news content resources locally function savedContent($, news_title) {
	$('dd.info').each(function (index, item) {
		var x = $(this).text();       
		var y = x.substring(0, 2).trim();
		if (y == '') {
			x = x + '\n';   
			//Add the news text content to the /data folder piece by piece, and name the file with the title of the news fs.appendFile('./data/' + news_title + '.txt', x, 'utf-8', function (err) {
				if (err) {
				console.log(err);
				}
			});
		}	
	})
}       
//The function is to store the crawled image resources locally function savedImg($,news_title) {
  $('dd.info img').each(function (index, item) {
        var img_title = $(this).parent().next().text().trim(); //Get the title of the image if(img_title.length>35||img_title==""){
         	img_title="Null";
        }
        var img_filename = img_title + '.jpg';
        var img_src = 'http://cs.whu.edu.cn' + $(this).attr('src'); //Get the URL of the image

		//Use the request module to initiate a request to the server to obtain image resources request.head(img_src,function(err,res,body){
		  if(err){
		    console.log(err);
		  }
		});
		request(img_src).pipe(fs.createWriteStream('./image/'+news_title + '---' + img_filename)); //Write the image to the local /image directory through streaming, and use the title of the news and the title of the image as the name of the image.
	})
}

fetchPage(url); //The main program starts running

var url = {
	hostname: 'cl.5fy.xyz',
	path: '/thread0806.php?fid=7',
	headers: {
		'Content-Type': 'text/html',
  	//Without this field, you cannot access it 'User-Agent': 'Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/46.0.2490.86 Safari/537.36',  
  }};

/*
* @Author: user
* @Date: 2018-04-28 19:34:50
* @Last Modified by: user
* @Last Modified time: 2018-04-30 21:35:26
*/
var http = require('http');
var fs = require('fs');
var cheerio = require('cheerio');
var request = require('request');
var iconv = require('iconv-lite');
var i = 0;
  //Used to determine whether to store or access var temp=0;
  let startPage=3;//Which page to start crawling from let page=startPage;
  let endPage=5;//Which page to crawl let searchText='';//Crawled keywords, all crawled by default, according to your needs //Initial url 
  var url = {
  hostname: '1024liuyouba.tk',
  path: '/thread0806.php?fid=16'+'&search=&page='+startPage,
  headers: {
    'Content-Type': 'text/html',
    //Without this field, you cannot access 'User-Agent': 'Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/46.0.2490.86 Safari/537.36',  
  }};
//Store the home page url
urlList=[];
//Encapsulates a layer of function function fetchPage(x) { 
  setTimeout(function(){  
    startRequest(x); },5000)
}
//First store the url of the interface to be accessed
function getUrl(x){
  temp++;
  http.get(x,function(res){
    var html = ''; 
    res.setEncoding('binary');
    res.on('data', function (chunk) {   
      html += chunk;
    });
    res.on('end', function () {
      var buf = new Buffer(html,'binary');
      var str=iconv.decode(buf,'GBK');
          var $ = cheerio.load(str); //Use cheerio module to parse HTML                
          $('tr.tr3 td.tal h3 a').each(function(){
            var search = $(this).text();
            if(search.indexOf(searchText)>=0){
            var nextLink="http://cl.5fy.xyz/" + $(this).attr('href');
            str1 = nextLink.split('-'); //Remove the Chinese characters after the url str = encodeURI(str1[0]); 
            urlList.push(str); }
          })
          page++;
          if(page<endPage){
            //Store the next page URL
            x.path='/thread0806.php?fid=16'+'&search=&page='+page,
            getUrl(x);
          }else if(urlList.length!=0){
            fetchPage(urlList.shift());
          }else{
            console.log('No keywords found!');
          }
        })
  }).on('error', function (err) {
    console.log(err);
  });

}
function startRequest(x) {
  if(temp===0){
    getUrl(x);     
  }   
  else{
     //Use http module to initiate a get request to the server http.get(x, function (res) {     
        var html = ''; //Used to store the entire HTML content of the requested web page res.setEncoding('binary');
        var titles = [];        
	     //Listen to the data event and fetch a chunk of data at a time res.on('data', function (chunk) {   
	      html += chunk;
	    });
	     //Listen for the end event. If the HTML of the entire webpage content is obtained, execute the callback function res.on('end', function () {
	    	var buf = new Buffer(html,'binary');
	    	var str=iconv.decode(buf,'GBK');
	        var $ = cheerio.load(str); //Use cheerio module to parse HTML
	        var news_item = {
	          	//Get the title of the article title: $('h4').text().trim(),
	        	//i is used to determine how many articles have been obtained i: i = i + 1,     
	      	};
	    console.log(news_item); //Print information var news_title = $('h4').text().trim();
		
	  	savedContent($,news_title); //Store the content and title of each article		
	  	savedImg($,news_title); //Store the image and title of each article		
	  	//If the access is not completed, continue to access if (urlList.length!=0) {
	    	fetchPage(urlList.shift());
	  	}
	});
}).on('error', function (err) {
    console.log(err);
  });
 }
}
       //The function is to store the crawled text content resources locally function savedContent($, news_title) {
	$("div.t2[style].tpc_content.do_not_catch").each(function (index, item) {
          var x = $(this).text();       
          x = x + '\n';   
		  //Add the news text content to the /data folder piece by piece, and name the file with the title of the news fs.appendFile('./data/' + news_title + '.txt', x, 'utf-8', function (err) {
			  if (err) {
			    console.log(err);
			  }
		  });
		})
 }
//The function is to store the crawled image resources locally function savedImg($,news_title) {
  //Create a folder fs.mkdir('./image/'+news_title, function (err) {
        if(err){console.log(err)}
      });
  $('.tpc_content.do_not_catch input[src]').each(function (index, item) {
        var img_title = index; //Add a number to each picture var img_filename = img_title + '.jpg';
        var img_src = $(this).attr('src'); //Get the URL of the image
//Use the request module to initiate a request to the server to obtain image resources request.head(img_src,function(err,res,body){
  if(err){
    console.log(err);
  }
});
setTimeout(function(){
  request({uri: img_src, encoding: 'binary'}, function (error, response, body) {
    if (!error && response.statusCode == 200) {
      fs.writeFile('./image/'+news_title+'/' + img_filename, body, 'binary', function (err) {
        if(err){console.log(err)}
      });
    }
  })
});
})
}
fetchPage(url); //The main program starts running