array.push doesn't seem to work on Nodejs Express

Question

I'm using a local database and Google API to build my own API, but I can't push objects into the "channels" array. I want the response to look something like this:

    [
       { id: 0, url: 'gwJ-mrP6_Ng', channelname: 'name1' },
       { id: 1, url: 'YPYwU2jeXIc', channelname: 'name2' },
       { id: 3, url: 'z3U0udLH974', channelname: 'name3' },
       { id: 2, url: 'AUHlDIuMLNY', channelname: 'name4' },
       { id: 4, url: 'vQEH_EksBbo', channelname: 'name5' }
    ]

And this is my code which I'm struggling with:

    app.get('/api/video/channels', (req, res) => {
        var channels = [];
        db.query(`SELECT video_url FROM videos`, (err, data) => {
            if (err) console.log(err);
            else {
                data.map((v, i) =>
                    axios.get(`https://www.googleapis.com/youtube/v3/videos?part=id%2C+snippet&id=${v.video_url}&key=${process.env.YT_API_KEY}`)
                        .then(res => channels.push({ "id": i, "url": v.video_url, "channelname": res.data.items[0].snippet.channelTitle }))
                )
                res.send(channels);
            }
        })
    })

console.log works, but the response always shows a blank array ( [] ). What is the problem with my code?

Thanks for your attention and help.

That is because you are trying to do some async stuff inside of the map callback. You are returning a response to the caller before that async stuff completes, so the response is always an empty array. — Enrico Massone, Feb 12 '22 at 09:08
Does this answer your question? [How to return the response from an asynchronous call](https://stackoverflow.com/questions/14220321/how-to-return-the-response-from-an-asynchronous-call) — jonrsharpe, Feb 12 '22 at 09:13
I get the concept of what I was doing wrong, thank you @EnricoMassone — Yumin Lee, Feb 12 '22 at 10:14
The question did help, although it feels a bit vague for me. But I get what the problem is, I'm just clearly not familiar with the concept. I should work on it. Thank you @jonrsharpe — Yumin Lee, Feb 12 '22 at 10:19

Mostafa Fakhraei · Accepted Answer · 2022-09-08T09:21:37.893

You have to use await to fulfill the result. try to change something like the below:

app.get('/api/video/channels', (req, res) => {
  var channels = [];
  db.query(`SELECT video_url FROM videos`, async (err, data) => {
    if (err) console.log(err);
    else {
      for (let i = 0; i < data.length; ++i) {
        let res = await axios.get(`https://www.googleapis.com/youtube/v3/videos?part=id%2C+snippet&id=${data[i].video_url}&key=${process.env.YT_API_KEY}`)
        channels.push({ "id": i, "url": data[i].video_url, "channelname": res.data.items[0].snippet.channelTitle });
      }
      res.send(channels);
    }
  })
})

array.push doesn't seem to work on Nodejs Express

1 Answers1