Metacharacters and parenthesis in regular expressions

Can anyone elaborate/translate this regular expression into English?

Thank you.

var g = "123456".match(/(.)(.)/);

I have noticed that the output looks like this:

12,1,2

and I know that dot means any character exc开发者_JAVA百科ept new line. But what does this actually do?

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A pair of parenthesis (without a ? as the first character, indicating other behaviour) will capture the contents to a group.

In your example, the first item in the array is the entire match, and subsequent items are any group matches.

It might be clearer if your code was something like:

var g = "123456".match(/.(.).(.)./);

This will match five characters, placing the second and fourth into groups 1 and 2 respectively, so outputting 12345,2,4

If you want pure grouping without capturing the content, use (?:...) syntax, the ?: part indicating a non-capturing group. (There are various assorted group things, like lookaheads and other fun stuff.)

Let me know if that is clear, or would further explanation help?

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It looks for two characters - any characters because of the dots - and 'captures' them so that you can look for the whole string that was matched, and for each of the substrings (captures) as well.