how to send information from javascript to flask route

1#python route
2@app.route('/this-route', methods=['GET', 'POST']):
3def thisRoute():
4    information = request.data
5    return "1"
6
7#javascript
8const URL = '/get-coordinates'
9const xhr = new XMLHttpRequest();
10sender = JSON.stringify([[1, 2, 3], [4, 5, 6], [7, 8, 9]])
11xhr.open('POST', URL);
12xhr.send(sender);