var request = require('request');

var fs = require('fs');

function downloadFile(uri, filename, callback){

    var stream = fs.createWriteStream(filename);

    request(uri).pipe(stream).on('close', callback);

}

if (!fs.existsSync('mp4')) {

    fs.mkdirSync('mp4');

}

console.log('Start download...');

for (let i = 1; i <= 22; i++) {

    const filename = 'mp4/NodeJS-lesson-' + i + '.mp4';

    downloadFile('https://cdn.nodelover.me/video_bucket/nodejs/' + i + '.mp4', filename, function() {

        console.log('Success: ' + filename + ' 下载完成！');

    });

}