To check whether input type "time" field is completed (09:00am) I have used a regular expression.
ng-pattern, you need to use
and if you need to avoid leading/trailing spaces, also add
See this regex demo.
(?:...)? optional non-capturing group is a wrapper for the whole pattern that becomes optional, i.e. can match an empty string.
^ anchor will only match at the start of the string, and
$ will anchor the match at the end of the string, so that an entire string should match.