I'm very new to programming. I'm trying to make a project where a locally hosted website, would fetch titles of the songs from a youtube playlist and then adds them to a list. So far, it fetches the first 50 items/titles, but then the loop stops. What goes wrong here?

let tracks = [];
let token = "";
let items;
let items_total;

function execute() {
        do {
        return gapi.client.youtube.playlistItems.list({
            "part": ["snippet"],
            "maxResults": 50,
            "pageToken": token,
            "playlistId": "id of the playlist"
        }).then(function(response) {
            let playlist = response;

            items = playlist.result.pageInfo.resultsPerPage;
            items_total = playlist.result.pageInfo.totalResults;
            token = playlist.result.nextPageToken;

            for (let i = 0; i < items; i++) {tracks.push(playlist.result.items[i].snippet.title)}
        },
        function(err) { console.error("Execute error", err); });
    } while (tracks.length < items_total)
}