Solution
const user = 0;
const flashcard_id = 1;
const req = axios.get(`http://127.0.0.1:5000/stat/${user}/${flashcard_id}`,{
headers: {'Access-Control-Allow-Origin': '*', 'X-Requested-With': 'XMLHttpRequest'},
})
from flask import request
@app.route('/stat/', methods=['GET', 'POST', 'OPTIONS'])
def stats():
user = request.args.get('user')
flashcard_id = request.args.get('flashcard_id')