製品POSTの接続

@app.route('/')
def home():
   return render_template('cosmetic.html')
   
@app.route('/product', methods=['POST'])
def saving():
    return jsonify({'result': 'success', 'msg':'POST 연결'})

cosmetic.htmlに関連付けられます

function postProduct() {
   $.ajax({
          type: "POST",
          url: "/product",
          data: {},
          success: function (response) { // 성공하면
                if (response["result"] == "success") {
                  alert(response["msg"]);
                    }
                }
            })
        }

<!-- JS -->
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js"
        integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q"
        crossorigin="anonymous"></script>