A useful script to download online course videos

download.js

// Imports the required libraries.
const https = require('https');
const fs = require('fs');

// Defines some constants.
const COURSE_HOMEPAGE = '<CHANGE_IT_HERE>';

// Parses the given JSON file regarding URLs.
const url_json = require('./restricted_files.json');
const url_list = url_json.data.getRestrictedFiles.urls;

// Filters according to the URL prefix.
const required_format = new RegExp(`${COURSE_HOMEPAGE}/video/.+/1080p/`);;
const filter_list = url_list.filter(url => url.match(required_format));
console.log(`We found ${filter_list.length} URLs which meet the required format.`);

// Parses the given JSON file regarding course content.
const course_json = require('./course_content.json');
const section_list = course_json.data.getCourse.sections;

// Iterates through each section of the course.
for (let i = 0; i < section_list.length; i++) {
	const current_section = section_list[i];

	// Creates a folder for the current section if not exists.
	const section_folder_name = `${current_section.sequence} ${current_section.title}`;
	if (!fs.existsSync(section_folder_name)) {
		fs.mkdirSync(section_folder_name);
	}
 
	for (let j = 0; j < current_section.components.length; j++) {
		// Finds the video with the matched URL.
		const current_component = current_section.components[j];
		const url_prefix = `${COURSE_HOMEPAGE}/video/${current_section.sectionIdentifier}_${current_component.componentIdentifier}/1080p/`;
		const found_url = filter_list.find(url => url.startsWith(url_prefix));

		// Downloads the video if found.
		if (found_url === undefined) {
			console.log(`Unable to find any URL with a prefix of ${url_prefix} with section_title=${current_section.title} component_title=${current_component.title}`);
			continue;
		}
		const output_file_name = `${current_section.sequence} ${current_section.title}/${current_component.sequence} ${current_component.title}.mp4`;
		const output_file = fs.createWriteStream(output_file_name);

		console.log(`Begins to download video from ${found_url} to ${output_file_name}:`);
		https.get(found_url, resp => {
			resp.pipe(output_file);
			output_file.on('finish', () => output_file.end());
		}).on('error', err => console.log(err));
	}
}