async/mapLimit函数理解

const phantom = require('phantom')

const express = require('express');

const app = express();

const axios = require('axios');

const isPlainObject = require('lodash/isPlainObject');

const qs = require('qs')

const Cookies = require('js-cookie')

const fs = require('fs');

const cheerio = require('cheerio');

const request = require('request');

//express服务器，

let server = app.listen(2000, function () {

    let host = server.address().address;

    let port = server.address().port;

    console.log('Your App is running at http://%s:%s', host, port);

});

//封装axios

const http = axios.create({

    timeout: 1000 * 180,

    withCredentials: true

})

/**

 * 请求拦截

 */

http.interceptors.request.use(config => {

    config.headers['Accept-Language'] = Cookies.get('language') || 'zh-CN'

    // console.log('token',Cookies.get('token'))

    // config.headers['Authorization'] = Cookies.get('token') || ''  //加token

    // if(config.headers['Authorization'] == '') {

    //     clearLoginInfo()

    //     router.replace({ name: 'login' })

    // }

    // 默认参数

    var defaults = {}

    // 防止缓存，GET请求默认带_t参数

    if (config.method === 'get') {

        config.params = {

            ...config.params,

            ...{'_t': new Date().getTime()}

        }

    }

    if (isPlainObject(config.params)) {

        config.params = {

            ...defaults,

            ...config.params

        }

    }

    if (isPlainObject(config.data)) {

        config.data = {

            ...defaults,

            ...config.data

        }

        if (/^application\/x-www-form-urlencoded/.test(config.headers['content-type'])) {

            config.data = qs.stringify(config.data)

        }

    }

    return config

}, error => {

    return Promise.reject(error)

})

/**

 * 响应拦截

 */

http.interceptors.response.use(response => {

    return response;

}, error => {

    console.error(error)

    return Promise.reject(error)

})

class stealData {

    constructor() {

        this.base_url = 'https://pvp.qq.com/web201605/wallpaper.shtml#%23%23'//爬取网址

        this.listAll = []

    }

    async init() {

        try {

            await this.geData()//打开网页

            // await this.getUrl()//打开网页

        } catch (e) {

            console.log(e);

        }

    }

    async geData() {

        await this.getUrl(0)

    }

    async getUrl(i) {

        console.log(i)

        let list = []

        let params = {

            page: i

        }

        http.get('https://apps.game.qq.com/cgi-bin/ams/module/ishow/V1.0/query/workList_inc.cgi?activityId=2735&sVerifyCode=ABCD&sDataType=JSON&iListNum=20&totalpage=0&iOrder=0&iSortNumClose=1&jsoncallback=jQuery17107547180061056307_1599185179163&iAMSActivityId=51991&_everyRead=true&iTypeId=2&iFlowId=267733&iActId=2735&iModuleId=2735&_=', {params: params}).then(res => {

            let a = JSON.parse(res.data.match(/({(\S*)})/)[1])

            this.down(a.List,i)

        })

    }

    sleep(time) {

        return new Promise((resolve) => {

            console.log(`自动睡眠中，${time / 1000}秒后重新发送请求......`)

            setTimeout(() => {

                resolve();

            }, time);

        });

    }//请求延迟时间，防止ip被封

    async down(src,index) {

        for (let i = 0;i<src.length;i++){

            let url = decodeURIComponent(src[i].sProdImgNo_7).replace("/200","/0")

            console.log('url',url)

            let ext = url.split('.').pop().substr(0,3)

            try {

                console.log(`开始写入第${i+index*20+1}张`)

                await request(url).pipe(fs.createWriteStream(`./Wangzhe/${new Date().getTime()}.${ext}`));

                await this.sleep(3000)//防止被封

                console.log(`写入成功`)

            }catch (e) {

                console.log('下载出错：',e)

            }

        }

        if(index<22){

            await this.getUrl(++index)

        }

    }

}

const thief = new stealData('xxx_url');

thief.init();

Node.js中理解asyncmap函数 ，爬取王者荣耀荣耀官网壁纸400多张的相关教程结束。