Can not insert multiple videos into a playlist - YouTube API v3

I am trying to add multiple videos to a playlist, but only one video is added to the playlist. I can successful create a playlist and insert a video to the playlist, but can not insert multiple videos to the playlist.

Below is a simple way that I am doing this. The function addTheseVideosToPlaylist() is specifically where I am failing. createPlaylist() and addToPlaylist() are also shown.

There is a global playlistId to keep track of created playlist.

var playlistId

I create a playlist like this:

function createPlaylist() {    var request = gapi.client.youtube.playlists.insert({        part: 'snippet,status',        resource: {            snippet: {                title: 'hard coded title',                description: 'Hard Coded Description'            },            status: {                privacyStatus: 'private'            }        }    });    request.execute(function(response) {        var result = response.result;        if (result) {            playlistId = result.id;            console.log("created playlist "+ playlistId)        }    });}

I add a video to the created playlist given a valid video id like below:

function addToPlaylist(id, startPos, endPos) {    console.log("In addToPlaylist with "+ id  +"sending to playlist : "+ playlistId);    var details = {        videoId: id,        kind: 'youtube#video'    }    var request = gapi.client.youtube.playlistItems.insert({        part: 'snippet',        resource: {            snippet: {                playlistId: playlistId,                resourceId: details            }        }    }).execute();}

The two above functions are fairly standard and work fine. However I have problems when adding multiple videos to a playlist like below in addTheseVideosToPlaylist(). I have an array of valid video ids and for each id, I will add it to the created playlist. The problem is that not all of the videos are added to the playlist, only one video is added.

function addTheseVideosToPlaylist() {    var links = ["wtLJPvx7-ys","K3meJyiYWFw","3TtVsy98ces"    ]    for(i = 0; i < links.length; i++)        addToPlaylist(links[i]);}

All in all, I am successful in creating a playlist and adding a video to the playlist, but when I try to insert multiple videos to a playlist by adding each link in an array, the playlist only contains one video.

How can I resolve this problem?