用TypeScript開發爬蟲程序

全局安裝typescript：

npm install -g typescript

目前版本2.0.3，這個版本再也不須要使用typings命令了。可是vscode捆綁的版本是1.8的，須要一些配置工做，看本文的處理辦法。

測試tsc命令：

tsc

建立要寫的程序項目文件夾：

mkdir test-typescript-spider

進入該文件夾：

cd test-typescript-spider

初始化項目：

npm init

安裝superagent和cheerio模塊：

npm i --save superagent cheerio

安裝對應的類型聲明模塊：

npm i -s @types/superagent --save
npm i -s @types/cheerio --save

安裝項目內的typescript（必須走這一步）：

npm i --save typescript

用vscode打開項目文件夾。在該文件夾下建立tsconfig.json文件，並複製如下配置代碼進去：

{
    "compilerOptions": {
        "target": "ES6",
        "module": "commonjs",
        "noEmitOnError": true,
        "noImplicitAny": true,
        "experimentalDecorators": true,
        "sourceMap": false,
     // "sourceRoot": "./",
        "outDir": "./out"
    },
    "exclude": [
        "node_modules"
    ]
}

在vscode打開「文件」-「首選項」-「工做區設置」
在settings.json中加入（若是不作這個配置，vscode會在打開項目的時候提示選擇哪一個版本的typescript）：

{
   "typescript.tsdk": "node_modules/typescript/lib"
}

建立api.ts文件，複製如下代碼進去：

import superagent = require('superagent');
import cheerio = require('cheerio');

export const remote_get = function(url: string) {

    const promise = new Promise<superagent.Response>(function (resolve, reject) {
        superagent.get(url)
            .end(function (err, res) {
                if (!err) {
                    resolve(res);
                } else {
                    console.log(err)
                    reject(err);
                }
            });
    });
    return promise;
}

建立app.ts文件，書寫測試代碼：

import api = require('./api');
const go = async () => {
    let res = await api.remote_get('http://www.baidu.com/');
    console.log(res.text);
}
go();

執行命令：

tsc

而後：

node out/app

觀察輸出是否正確。

如今嘗試抓取http://cnodejs.org/的第一頁文章連接。
修改app.ts文件，代碼以下：

import api = require('./api');
import cheerio = require('cheerio');

const go = async () => {
    const res = await api.remote_get('http://cnodejs.org/');
    const $ = cheerio.load(res.text);
    let urls: string[] = [];
    let titles: string[] = [];
    $('.topic_title_wrapper').each((index, element) => {
        titles.push($(element).find('.topic_title').first().text().trim());
        urls.push('http://cnodejs.org/' + $(element).find('.topic_title').first().attr('href'));
    })
    console.log(titles, urls);
}
go();

觀察輸出，文章的標題和連接都已獲取到了。

如今嘗試深刻抓取文章內容

import api = require('./api');
import cheerio = require('cheerio');

const go = async () => {
    const res = await api.remote_get('http://cnodejs.org/');
    const $ = cheerio.load(res.text);
    $('.topic_title_wrapper').each(async (index, element) => {
        let url = ('http://cnodejs.org' + $(element).find('.topic_title').first().attr('href'));
        const res_content = await api.remote_get(url);
        const $_content = cheerio.load(res_content.text);
        console.log($_content('.topic_content').first().text());
    })

}
go();

能夠發現由於訪問服務器太迅猛，致使出現不少次503錯誤。
解決：
添加helper.ts文件：

export const wait_seconds = function (senconds: number) {
    return new Promise(resolve => setTimeout(resolve, senconds * 1000));
}

修改api.ts文件爲：

import superagent = require('superagent');
import cheerio = require('cheerio');

export const get_index_urls = function () {
    const res = await remote_get('http://cnodejs.org/');
    const $ = cheerio.load(res.text);
    let urls: string[] = [];
    $('.topic_title_wrapper').each(async (index, element) => {
        urls.push('http://cnodejs.org' + $(element).find('.topic_title').first().attr('href'));
    });
    return urls;
}
export const get_content = async function (url: string) {
    const res = await remote_get(url);
    const $ = cheerio.load(res.text);
    return $('.topic_content').first().text();
}

export const remote_get = function (url: string) {

    const promise = new Promise<superagent.Response>(function (resolve, reject) {

        superagent.get(url)
            .end(function (err, res) {
                if (!err) {
                    resolve(res);
                } else {
                    console.log(err)
                    reject(err);
                }
            });
    });
    return promise;
}

修改app.ts文件爲：

import api = require('./api');
import helper = require('./helper');
import cheerio = require('cheerio');

const go = async () => {
    let urls = await api.get_index_urls();
    for (let i = 0; i < urls.length; i++) {
        await helper.wait_seconds(1);
        let text = await api.get_content(urls[i]);
        console.log(text);
    }
}
go();

觀察輸出能夠看到，程序實現了隔一秒再請求下一個內容頁。

如今嘗試把抓取到的東西存到數據庫中。
安裝mongoose模塊：

npm i mongoose --save
npm i -s @types/mongoose --save

而後創建Scheme。先建立models文件夾：

mkdir models

在models文件夾下建立index.ts：

import * as mongoose from 'mongoose';

mongoose.connect('mongodb://127.0.0.1/cnodejs_data', {
    server: { poolSize: 20 }
}, function (err) {
    if (err) {
        process.exit(1);
    }
});

// models
export const Article = require('./article');

在models文件夾下建立IArticle.ts:

interface IArticle {
    title: String;
    url: String;
    text: String;
}
export = IArticle;

在models文件夾下建立Article.ts:

import mongoose = require('mongoose');
import IArticle = require('./IArticle');
interface IArticleModel extends IArticle, mongoose.Document { }

const ArticleSchema = new mongoose.Schema({
    title: { type: String },
    url: { type: String },
    text: { type: String },
});

const Article = mongoose.model<IArticleModel>("Article", ArticleSchema);
export = Article;

修改api.ts爲：

import superagent = require('superagent');
import cheerio = require('cheerio');
import models = require('./models');
const Article = models.Article;

export const get_index_urls = async function () {
    const res = await remote_get('http://cnodejs.org/');

    const $ = cheerio.load(res.text);
    let urls: string[] = [];
    $('.topic_title_wrapper').each((index, element) => {
        urls.push('http://cnodejs.org' + $(element).find('.topic_title').first().attr('href'));
    });
    return urls;

}
export const fetch_content = async function (url: string) {
    const res = await remote_get(url);

    const $ = cheerio.load(res.text);
    let article = new Article();
    article.text = $('.topic_content').first().text();
    article.title = $('.topic_full_title').first().text().replace('置頂', '').replace('精華', '').trim();
    article.url = url;
    console.log('獲取成功：' + article.title);
    article.save();

}
export const remote_get = function (url: string) {

    return new Promise<superagent.Response>((resolve, reject) => {
        superagent.get(url)
            .end(function (err, res) {
                if (!err) {
                    resolve(res);
                } else {
                    reject(err);
                }
            });
    });
}

修改app.ts爲：

import api = require('./api');
import helper = require('./helper');
import cheerio = require('cheerio');

(async () => {

    try {
        let urls = await api.get_index_urls();
        for (let i = 0; i < urls.length; i++) {
            await helper.wait_seconds(1);
            await api.fetch_content(urls[i]);
        }
    } catch (err) {
        console.log(err);
    }

    console.log('完畢！');

})();

執行

tsc
node out/app

觀察輸出，並去數據庫檢查一下
能夠發現入庫成功了！

補充：remote_get方法的改進版，實現錯誤重試和加入代理服務器.
放棄了superagent庫，用的request庫，僅供參考：

//config.retries = 3;
let current_retry = config.retries || 0;
export const remote_get = async function (url: string, proxy?: string) {
    //每次請求都先稍等一下
    await wait_seconds(2);
    if (!proxy) {
        proxy = '';
    }
    const promise = new Promise<string>(function (resolve, reject) {
        console.log('get: ' + url + ',  using proxy: ' + proxy);
        let options: request.CoreOptions = {
            headers: {
                'Cookie': '',
                'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.143 Safari/537.36',
                'Referer': 'https://www.baidu.com/'
            },
            encoding: 'utf-8',
            method: 'GET',
            proxy: proxy,
            timeout: 3000,
        }
        request(url, options, async function (err, response, body) {
            console.log('got:' + url);
            if (!err) {
                body = body.toString();
                current_retry = config.retries || 0;
                console.log('bytes:' + body.length);
                resolve(body);
            } else {
                console.log(err);
                if (current_retry <= 0) {
                    current_retry = config.retries || 0;
                    reject(err);
                } else {
                    console.log('retry...(' + current_retry + ')')
                    current_retry--;
                    try {
                        let body = await remote_get(url, proxy);
                        resolve(body);
                    } catch (e) {
                        reject(e);
                    }
                }
            }
        });
    });
    return promise;
}

另外，IArticle.ts和Article.ts合併爲一個文件，可能更好，能夠參考我另外一個model的寫法：

import mongoose = require('mongoose');

interface IProxyModel {
    uri: string;
    ip: string;
    port:string;
    info:string;
}
export interface IProxy extends IProxyModel, mongoose.Document { }

const ProxySchema = new mongoose.Schema({
    uri: { type: String },//
    ip: { type: String },//
    port: { type: String },//
    info: { type: String },//
});
export const Proxy = mongoose.model<IProxy>("Proxy", ProxySchema);

導入的時候這麼寫就好了：

import { IProxy, Proxy } from './models';

其中Proxy能夠用來作new、find、where之類的操做:

let x = new Proxy();
let xx = await Proxy.find({});
let xxx = await Proxy.where('aaa',123).exec();

而IProxy用於實體對象的傳遞，例如

function xxx(p:IProxy){
}