组合以及单例模式优化代码

组合设计模式

• 将爬虫读取html以及写入文件的操作单独抽离出来复用 （crowller.ts）
• 另外的分析爬取内容按照不同需求单独生成自己的分析器（analyze.ts）
• 在crowller.ts中调用不同的分析器analyze.ts，实现逻辑的组合设计

单例模式

• 分析器analyze.ts只需要一次初始化即可，采用单例模式来实现。

/* 
*  crowller.ts：爬虫器
*/

// 抓取html
import superagent from 'superagent';

import fs from 'fs';
import path from 'path';
import SelfAnalyzer from './analyzer';

export interface Analyzer {
  analyze: (html: string, filePath: string) => string;
}

class Crowller {
  private filePath = path.resolve(__dirname, '../dist/data.json');
  constructor(private url: string, private analyzer: Analyzer) {
    this.init();
  }

  private async getHtml() {
    const res = await superagent.get(url);
    return res.text;
  }

  private writeFile(fileContent: string) {
    fs.writeFileSync(this.filePath, fileContent);
  }

  private async init() {
    const html = await this.getHtml();
    const fileContent = this.analyzer.analyze(html, this.filePath);
    this.writeFile(fileContent);
  }
}

const secret = 'x3b174jsx';
const url = `http://www.dell-lee.com/typescript/demo.html?secret=${secret}`;

const analyzer = SelfAnalyzer.getInstance();
new Crowller(url, analyzer);

/* 
*  anylyze.ts： 分析器
*/

// 获取节点元素
import * as cheerio from 'cheerio';

import fs from 'fs';

import { Analyzer } from './crowller';

interface Course {
  title: string;
  count: number;
}

interface CourseInfo {
  time: number;
  data: Course[];
}

interface FileContent {
  [prop: number]: Course[];
}

export default class SelfAnalyzer implements Analyzer {
  private static instance: SelfAnalyzer;
  private constructor() {}
  static getInstance() {
    if (!SelfAnalyzer.instance) {
      SelfAnalyzer.instance = new SelfAnalyzer();
    }
    return SelfAnalyzer.instance;
  }
  private getCourseInfo(html: string) {
    const $ = cheerio.load(html);
    const $courseItems = $('.course-item');
    const courseInfos: Course[] = [];
    $courseItems.map((index, ele) => {
      const descs = $(ele).find('.course-desc');
      const title = descs.eq(0).text();
      const count = parseInt(descs.eq(1).text().split('：')[1]);
      courseInfos.push({ title, count });
    });

    return {
      time: new Date().getTime(),
      data: courseInfos,
    };
  }

  private genJSON(courseInfo: CourseInfo, filePath: string) {
    let fileContent: FileContent = {};
    if (fs.existsSync(filePath)) {
      try {
        fileContent = JSON.parse(fs.readFileSync(filePath, 'utf-8'));
      } catch (e) {
        console.log('无法解析');
      }
    }
    fileContent[courseInfo.time] = courseInfo.data;
    return fileContent;
  }

  analyze(html: string, filePath: string) {
    const courseInfo = this.getCourseInfo(html);
    const fileContent = this.genJSON(courseInfo, filePath);
    return JSON.stringify(fileContent);
  }
}