social script video downloader

javascript:
var host = window.location.hostname;
var pathname = window.location.pathname;
var fullurl = host + pathname;
var https_host = "https://" + host + pathname;
var ps = fullurl.split("/")[1];
switch (host) {
    case "www.instagram.com":
        switch(ps) {
            case "p":
                    var linkvid = document.getElementsByClassName("tWeCl")[0];
                    if(linkvid == undefined){
                    var length_photo = document.getElementsByClassName("FFVAD").length;
                    var linkins = length_photo - 1;
                    var link_photo = document.getElementsByClassName("FFVAD")[linkins].currentSrc;
                    window.open(link_photo, '_blank');
                        
                    }else{
                        var linkvid = linkvid.currentSrc;
                        window.open(linkvid, '_blank');
                    }
            break;
            case "stories":
                    var photo = document.getElementsByClassName('y-yJ5')[0].src;
                if(photo == null){
                    var video = document.getElementsByClassName('y-yJ5')[2].currentSrc;
                    window.open(video, '_blank'); 
                }
                else{
                    window.open(photo , '_blank');
                }
            break;
            default:
                
            }
    break;
    case "www.facebook.com":
              switch (ps) {
                  case "stories":
                      var link_videofb = document.getElementsByClassName("k4urcfbm l9j0dhe7 qowsmv63 datstx6m j83agx80")[0].getElementsByTagName("video")[0].currentSrc;
                      window.open(link_videofb, '_blank');
                      break;
                  case "watch":
                        var js = document.documentElement.innerHTML;
                        var start = js.search('"hd_src":"');
                        var end = js.search('","sd_src"');
                        var getvideofb = js.substring(start+51,end);
                        var xulylink = getvideofb.replace("\\","");
                        var xulylink = xulylink.replace("\\","");
                        var videofb = "https://scontent-lga3-1.xx.fbcdn.net"+xulylink;
                        window.open(videofb , '_blank');
                  break;
                  case "groups":
                        var jsgr = document.documentElement.innerHTML;
                        var start = jsgr.search(',hd_src:"');
                        var end = jsgr.search('",sd_src:"');
                        var getvideogr = jsgr.substring(start+9,end);
                        window.open(getvideogr , '_blank');

                  break;
                 default:
                        document.getElementsByClassName('_7yy')[0].innerHTML;
        break;
              }  
        break;
                default:
                        var tumblr = document.querySelector("meta[property='og:video']").getAttribute("content");
                        window.open(tumblr , '_blank');
        break;
}