From fc290cf22cf6af001b8979bb2e4e71f40285ea13 Mon Sep 17 00:00:00 2001 From: Aakash Panchal <51417248+Aakash-Panchal27@users.noreply.github.com> Date: Sun, 8 Mar 2020 13:00:23 +0530 Subject: [PATCH] Create named_groups.html --- Akash Articles/RegEx/named_groups.html | 90 ++++++++++++++++++++++++++ 1 file changed, 90 insertions(+) create mode 100644 Akash Articles/RegEx/named_groups.html diff --git a/Akash Articles/RegEx/named_groups.html b/Akash Articles/RegEx/named_groups.html new file mode 100644 index 0000000..8ec64f8 --- /dev/null +++ b/Akash Articles/RegEx/named_groups.html @@ -0,0 +1,90 @@ + + + + + + + + + + + + +

Named Groups

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Regular expressions with lots of groups and backreferencing can be difficult to maintain, as adding or removing a capturing group in the middle of the regex turns to change the numbers of all the groups that follow the added or removed group.

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In regex, we have facility of named groups, which solves the above issue. Let's look at it.

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We can name a group by putting ?<name> just after opening the paranthesis representing a group. For example, (?<year>\d{4}) is a named group.

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Below is a code, we have already looked in capturing groups part. You can see, the code is more readable now.

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    var str = "2020-01-20";
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+		    // Pattern string
+		    var pattern = /(?<year>\d{4})-(?<month>\d{2})-(?<day>\d{2})/g;
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+		    //                ^       ^       ^
+		    //group-no:   1       2       3
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+		    // Data replacement using $<group_name>
+		    var ans=str.replace(pattern, '$<day>-$<month>-$<year>');
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+		    console.log(ans);
+		    // Output will be: 20-01-2020
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Backreference syntax for numbered groups works for named capture groups as well. \k<name> matches the string that was previously matched by the named capture group name, which is a standard way to backreference named group.

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