In Angular 8 I need to validate if a string is equal to yes allowing:
- Spaces, and only spaces, before and after. 
- Case insensitive so - Yes,- YES, ... would be allowed.
I tried the following regex Regexr:
^(?i)yes$
But I get an error:
(?i) is not allowed in Javascript
And I am not allowing spaces between and after.
 
    