Can python flask save 'static' somewhere?

I am coding simple web app by python flask. This is my code :

app = Flask(__name__)
app.static_folder = 'static'
@app.route("/", methods=['GET'])
def main() :
    return render_template("Myhtml.html")

But, when i change my .js file in 'static' folder and reload page. My change is no there ?! Is it possible. I cant find solution.