I want to extract characters in parentheses and return empty characters if the result is empty.

Find the range bounded by () from the string passed by the argument str and return the string for that part.

• () returns empty characters if the contents are empty.
• () returns the contents of the first parenthesis found if there are multiple
• ()(Quickest match)
Returns null if
• () is not found.

If () is empty, I want to return an empty character, but it says null.
Could you please let me know?

function extractStr(str){
  varret=/\(.+?)\)/.exec(str);
  return ret?ret[1]: null;
}