Why is this form not submitted twice when hitting the button twice?

Question

Edit 25.07.2018: As Pawnesh Kumar said in the answer, this seems to be a browser issue. If I hit the button multiple times in Firefox the below script will only

Answer 1

It is a browser thing.

I believe you are talking about the situation when a user clicks multiple times on the button. While in the background the page start reloading.

When we hit the submit button browser send the request to server. Until the response receive some browser show the old(expired) page while some simple clean the view.

In Firefox, it won't fire any event in spite of clicking many times. Wherein Chrome it submit the request to the server every time user click.

So, the bottom line it is the way the browser handles things. Your logs also showing you were using Firefox so that the case.