Person requested to share some script I used.

index.js

/* -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.
* File Name   : index.js
* Created at  : 2018-05-27
* Updated at  : 2018-05-27
* Author      : jeefo
* Purpose     :
* Description :
_._._._._._._._._._._._._._._._._._._._._.*/
// ignore:start
"use strict";

/* globals */
/* exported */

// ignore:end

var fs      = require("fs");
var async   = require("async");
var request = require('request');
var cheerio = require('cheerio');

var url = 'https://doc.lagout.org/Others/Game%20Development/Programming/';

var download = function(url, filename, callback){
    request.get(url)
		.on('error', function(err) { console.log(err); })
		.pipe(fs.createWriteStream(filename))
		.on('close', callback);
};

request(url, function(err, resp, body){
	var $ = cheerio.load(body);
	var links = $('pre > a'); //jquery get all hyperlinks
	var books = [];

	$(links).each(function(i, link){
		if (i === 0) { return; }
		var uri = $(link).attr('href');

		books.push({
			url  : `${ url }${ uri }`,
			name : decodeURIComponent(uri)
		});
	});

	async.eachSeries(books, function (book, callback) {
		download(book.url, book.name, function (err) {
			if (err) {
				console.error("ERROR");
				console.error(book);
				console.error(err);
				process.exit();
			} else {
				console.log(`Download: ${ book.name }`);
				callback();
			}
		});
	}, function () {
		console.log("Done");
	});
});