Javascript函数在NodeJs（Express）中返回了一个未定义的值

Question

我正在编写一个从youtube下载视频的nodejs函数。无论视频是否已下载，该功能都应返回。下面的代码应该打印 Invalid Link ，但我得到 undefined 。我是NodeJs和Js的新手。请帮助。

var youtubedl = require('youtube-dl');
var fs = require('fs');

var videoName="";
var results="";

function getVideo(videoLink) {

    var video = youtubedl(videoLink);

    video.on('error',function (err) {
    //console.log(err.message);
    results = "Invalid Link"
    });

    video.on('info', function (info) {
        console.log('Download started');
        //console.log('Title: ' + info.title);
        //console.log('Description: ' + info.description);
        //console.log('size: ' + info.size);
        videoName = info.title;
    });

    video.on('end', function () {
        //console.log("Finished Downloading Video");
        results = "Finished Downloading Video";
    });

    video.pipe(fs.createWriteStream('youtubeVideo.mp4'));
    return results;
};

console.log(getVideo("Some Invalid Link"));

module.exports.getVideo = getVideo;