如何从下拉框选择中访问要在url_for中使用的值

<select id="mySelect">
  <option value="value1">Option 1</option>
  <option value="value2">Option 2</option>
  <option value="value3">Option 3</option>
</select>

var selectedValue = document.getElementById("mySelect").value;

var xhr = new XMLHttpRequest();
xhr.open("GET", "/your-backend-url?selectedValue=" + selectedValue, true);
xhr.send();

from flask import Flask, request

app = Flask(__name__)

@app.route("/your-backend-url")
def your_backend_function():
    selected_value = request.args.get("selectedValue")
    # 使用selected_value构建URL或进行其他操作
    return "Your response"

if __name__ == "__main__":
    app.run()