批量導出某個簡書用戶的全部文章列表和文章超連接

簡書改版後，根據文章標題搜索文章的功能就不見了。

雖然簡書提供了批量下載文章的功能，可是下載到本地的文章都是markdown格式的，不包含文章的連接，這不知足個人需求。

既然我是程序員，沒有這個功能我就本身實現一個。

打開簡書首頁，發現默認只顯示8篇文章，用鼠標滑動到屏幕底部後，會觸發一個懶加載事件，到後臺讀取更多的文章列表，因此文章讀取在服務器端是採起的分頁實現。

打開Chrome開發者工具，觀察網絡請求，請求url中99b8712e8850是我簡書用戶id，page=2，3，4這些是分頁代碼。

每頁的文章內容以html格式包含在響應結構裏：

我關心的只是文章標題和文章連接，如上圖高亮字段所示。

最開始我寫了一個nodejs應用，代碼以下：

var request = require('request');
var jsdom = require("jsdom");
var JSDOM = jsdom.JSDOM;
const PREFIX = "https://www.jianshu.com";
const PAGE = "https://www.jianshu.com/u/99b8712e8850?order_by=shared_at&page=";
const MAX = 2;

var mArticleResult = new Map();
var pageNumber;
/* a given article: https://www.jianshu.com/p/963cd23fb092
  value got from API: /p/5c1d0319dc42
*/
var lastPageReached = false;
var url = "";

var aHandlers = [];

// use limited for loop to ease testing
for(var i = 0; i < MAX; i++){
  pageNumber = i + 1;
  var url = PAGE + pageNumber;
  // console.log("current page: " + url);
  var pageOptions = {
        url: url,
        method: "GET",
        headers: {
            "Accept": "text/html"
        }
  };
  aHandlers.push(getArticles(pageOptions, pageNumber));
  if( lastPageReached)
    break;
}

console.log("promise handler size: " + aHandlers.length);

Promise.all(aHandlers).then(function(){
  var articleIndex = 0;
  for (var [key, value] of mArticleResult) {
    console.log("Article[" + articleIndex++ + "]: " + key + " = " + value);
  }
  console.log("done");
}
  );

function getArticles(pageOptions, pageNumber) {
  return new Promise(function(resolve,reject){
      var requestC = request.defaults({jar: true});

      requestC(pageOptions,function(error,response,body){
        if( error){
          console.log("error: " + error);
          resolve(error);
        }
        var document = new JSDOM(body).window.document;
        var content = document.getElementsByTagName("li");

        for( var i =0; i < content.length; i++){
          var li = content[i];
          var children = li.childNodes;
          for( var j = 0; j < children.length; j++){
              var eachChild = children[j];
              if( eachChild.nodeName == "DIV"){
                var grandChild = eachChild.childNodes;
                for( var k = 0; k < grandChild.length; k++){
                  var grand = grandChild[k];
                  if( grand.nodeName == "A"){
                    var fragment = grand.getAttribute("href");
                    if( fragment.indexOf("/p") < 0)
                      continue;
                    console.log("title: " + grand.text);
                    var wholeURL = PREFIX + fragment;
                    console.log("url: " + wholeURL);
                    if( mArticleResult.has(grand.text)){
                      lastPageReached = true;
                      console.log("article size: " + mArticleResult.size);
                      resolve(pageNumber);
                    }
                    mArticleResult.set(grand.text, wholeURL);
                  }
                }
              }
          }
        }// end of outer loop
        resolve(pageNumber);
      }); 
     });
}

原理就是使用nodejs的request module，向簡書網站同時發起多個請求，每一個請求讀取一頁的簡書文章。

後來發現這種方法在併發請求數大於10個的時候就沒法工做，簡書網站會拒絕該類請求，返回HTTP 429狀態碼。

因此最後我採用了最簡單的同步請求實現，使用了nodejs提供的sync-request在循環裏發起請求。

var request = require("sync-request");
var jsdom = require("jsdom");
var JSDOM = jsdom.JSDOM;
var textEncoding = require('text-encoding'); 
var textDecoder = textEncoding.TextDecoder;

const PREFIX = "https://www.jianshu.com";
const PAGE = "https://www.jianshu.com/u/99b8712e8850?order_by=shared_at&page=";
const MAX = 100;

var mArticleResult = new Map();
var lastPageReached = false;
var pageNumber;
/* a given article: https://www.jianshu.com/p/963cd23fb092
  value got from API: /p/5c1d0319dc42
*/

try {
    // use limited for loop to ease testing
    for (var i = 0; i < MAX; i++) {
        if( lastPageReached)
          break;
        pageNumber = i + 1;
        var url = PAGE + pageNumber;
        console.log("current page: " + url);
        var response = request('GET', url);
        var html = new textDecoder("utf-8").decode(response.body);
        handleResponseHTML(html);
    }
} 
catch (e) {

}

var articleIndex = 0;
var resultHTML = "<html>";

const fs = require('fs');

/*
<HTML>
<p>
<a href="https://www.baidu.com">eee</a>
</p>

<p><a>22</a></p>
<p><a>33</a></p>
</HTML>
*/

var index = 1;
for (var [key, value] of mArticleResult) {
    var article = "<p><a href=\"" + key + "\">" + 
    index++ + ". " + value + "</a></p>" + "\n";
    resultHTML = resultHTML + article;
    console.log("Article[" + articleIndex++ + "]: " + value + " = " + key);
}

resultHTML = resultHTML + "</html>";

var pwd = process.cwd() + "/jianshu.html";

fs.appendFileSync(pwd, resultHTML);

console.log("done");



function handleResponseHTML(html) {
    var document = new JSDOM(html).window.document;
    var content = document.getElementsByTagName("li");

    for (var i = 0; i < content.length; i++) {
        var li = content[i];
        var children = li.childNodes;
        for (var j = 0; j < children.length; j++) {
            var eachChild = children[j];
            if (eachChild.nodeName == "DIV") {
                var grandChild = eachChild.childNodes;
                for (var k = 0; k < grandChild.length; k++) {
                    var grand = grandChild[k];
                    if (grand.nodeName == "A") {
                        var fragment = grand.getAttribute("href");
                        if (fragment.indexOf("/p") < 0)
                            continue;
                        // console.log("title: " + grand.text);
                        var wholeURL = PREFIX + fragment;
                        // console.log("url: " + wholeURL);
                        if (mArticleResult.has(wholeURL)) {
                            lastPageReached = true;
                            console.log("article size: " + mArticleResult.size);
                            return;
                        }
                        mArticleResult.set(wholeURL, grand.text);
                    }
                }
            }
        }
    }
}

這個nodejs應用執行後，會在本地生成一個html文件，包含每篇文章的標題和超連接。

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