I have next JS-code:
var str = 'some string';
var rexp = /^([^#]+)/;
var matchArr = str.match(rexp);
matchArr then contains two items matchArr[0] = 'some string' and matchArr[1] = 'some string'; Whereas I'm expecting the array with only one item.
I can't understand this behavior. When I remove parentheses, then matchArr contains only one match. Why this happens, does anybody can explain?
When you use capturing parentheses in your regular expression, it adds an item to the returned results array for the overall match and each set of capturing parentheses.
matchArr[0] is everything that was matched.
matchArr[1] is what matches in the first set of capturing parentheses
matchArr[2] is what matches in the second set of capturing parentheses
and so on
So, in your regex /^([^#]+)/, there is no difference between matchArr[0] and matchArr[1] because everything that matches is in the capturing parentheses.
If you did this:
var str = 'some string';
var rexp = /^some([^#]+)/;
var matchArr = str.match(rexp);
You would find that:
matchArr[0] == "some string";
matchArr[1] == " string";
because there are parts of the match that are not in the capturing parentheses.
Or if you did this:
var str = 'some string';
var rexp = /^(some)([^#]+)/;
var matchArr = str.match(rexp);
You would find that:
matchArr[0] == "some string";
matchArr[1] == "some"
matchArr[2] == " string";
