Check file exists before creating Google Drive API - node.js

Question

I have put together a script that creates a file in a folder on Google Drive, when I make amendments to that file and push it back up it will create a new version (which is obviously correct). What I would like to do is check that the file exists first (by name if I can) and then update that file if exists or create new if it does not.
# index.js
const google = require('googleapis');
const fs = require('fs');
const config = require('./creds.json');
const drive = google.drive('v3');
const targetFolderId = "123456789"
const jwtClient = new google.auth.JWT(
config.client_email,
null,
config.private_key,
['https://www.googleapis.com/auth/drive'],
null
);
jwtClient.authorize((authErr) => {
if (authErr) {
console.log(authErr);
return;
}
const fileMetadata = {
name: './file.xlsx,
parents: [targetFolderId]
};
const media = {
mimeType: 'application/vnd.ms-excel',
body: fs.createReadStream('./file.xlsx' )
};
drive.files.create({
auth: jwtClient,
resource: fileMetadata,
media,
fields: 'id'
}, (err, file) => {
if (err) {
console.log(err);
return;
}
console.log('Uploaded File Id: ', file.data.id);
});
});
Update
As D Levine mentions I can use drive.files.list but I am having problems finding a file. I set up a service account so not sure if that makes a difference. My code is below but all I get at the moment is undefined returned. I would also like to search within specific folders but can't seem to find this option anywhere.
// Check File exists
drive.files.list({
auth: jwtClient,
spaces: 'drive',
q: "name='liverpool_away.xlsx'",
pageSize: 10,
fields: "nextPageToken, files(id, name)"
}, function(err, response) {
if (err) {
console.log('The API returned an error: ' + err);
return;
}
var files = response.files;
console.log("Files: " + files);
if (files.length == 0) {
console.log('No files found.');
} else {
console.log('Files:');
for (var i = 0; i < files.length; i++) {
var file = files[i];
console.log('%s (%s)', file.name, file.id);
}
}
});

Answer 1

You can find if a file exists by searching by name with driveService.files().list(). If you receive 1 result, then that is the file that you were looking for and you can get the file ID. If you receive 0 results, then the file does not exist.
A page describing how to search is here (with example code at the bottom): https://developers.google.com/drive/v3/web/search-parameters
The REST endpoint is documented here: https://developers.google.com/drive/v3/reference/files/list