[js sdk]How to close the PayPal popup opened by click paypal button

[ethan59]

I rendered a paypal standard button in a spa page. it opened a popup when I click the button. I want to close the popup in some case such as user click the router back button in a spa page. How do I code it?  I have tried button.close, but it did not work

 By the way, it does not open paypal popup but outlined the button if I click it immediately when the button rendered