regex to capture optional group based on optional substring

Question

I want to create a regex to capture optional group based on optional substring. Examples could be:

DATEF[[%d/%m/%Y %H:%M 
DATEF[[%H:%M]]
DATEF
TIME

etc.

I would like the DATE and parameter %H:%M to be captured. The expression (.*?)\\[\\[(.*?)\\]\\] works with parameters, but the optional excluded strings fail and return null.

Answer 1

i would suggest this one:

/^([a-zA-Z]+)(?:\\[\\[([^\\]]+)\\]\\])?$/

group 1 holds the functionname, and if a [[ is present, group 2 captures everything between [[ and ]] , if the squares are not present, group 2 won't be present at all.

EDIT:

Note the outer non-capturing group contains a capturing group:

/^([a-zA-Z]+)         #captures the command
    (?:\[\[           #matches, but not captures the opening brackets
        ([^\]]+?)     #captures the content of the brackets
    \]\])?            #matches the closing brackets
$/x