What does "(?!$)" inside a regexp mean?

In a section of Sevelte tutorial, there’s a piece of code like this:

view = pin ? pin.replace(/\d(?!$)/g, '•') : 'enter your pin';

I know \d means a digit, but can’t figure out what (?!$) means.

(And because it’s composed of all punctuation, I can’t manage to google for an explanation.)

Please help, thanks.

>Solution :

• \d matches all digits
• ?! means ‘Negative Lookahead’
• $ matches the end of a string

So when \d(?!$) is used, it matches all digits before the last character

In this string:

$$//www12.example@news.com<~>998123000dasas00–987

This will be matched (7 will not because it is the last character):

129981230000098

Referred to this answer
and Regex Cheat Sheet