How do I Remove particular dublicate characters from string in javascript?

I’m doing a mail project and it has reply function to particular email. There are pre-written things in reply email like Re: ${Subject of the email}

There is Re: that repeats after 2nd reply so i wrote this in my function in order to remove it:

subject = document.querySelector('#compose-subject').value;

  if (subject.includes("Re: ")){
              subject = subject.replace("Re: ", "");
          }

How do i make this part of code work only for dublicates? Like Re: Re: (removing 2nd Re: )

Now it works even on first Re: and just removing it.

How can i implement it?

>Solution :

You can use a regexp to replace any number of repeated Re:s with any number of spaces after them with a single Re: :

var subject = document.querySelector('#compose-subject').value;
subject = subject.replace(/^(Re:\s+)+/g, 'Re: ');

You can add the i flag for case insensitivity too (i.e. /gi instead of /g).