What's the intent of () inside the regex? Thanks.
pattern.replace(/\{(\d+)\}/g,
function(pattern, index) {
return args[index].toString();
});
PS: args is something like ["3", "dl1", "42"]
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2 Answers
It is used to manage grouping.
The purpose of grouping is to make backreferences on searches & replaces. Using regex you can make that Jhon Doe becomes Doe, Jhon.
To achieve that, you would use a Regex (\w*) (\w*) with two grups, and replace it for $2, $1
Usually, the first group (0) references the whole match of the regex, being the other groups numbered according to the order where they are in your expression.
4 Comments
CurtainDog
+1: But I would add that not all groups are capturing groups. Some just affect the operation of *,+,?,| etc
Ricky
Hi can u make a example for your answer? Thanks.
SoulWanderer
I use a regex (Java format, it is quite similar to Javascript) to parse jdbc oracle connection chain:
jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=test)(PORT=1521))(CONNECT_DATA=(SID = sidbbdd)) I need it to fin the host, so I would write .*@.*HOST=(\w*)\).* This regex will ignore pretty much everything until it finds HOST= then, it will find everything until it finds ) and ignore the rest of the chain. To reference the part of my host I would use $1, which would return test.SoulWanderer
Should I need further matchings of subsets of the regex, I would use more groups, for instance
(.*@.*)HOST=(\w*)\)(.*) would return: $0 --> jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=test)(PORT=1521))(CONNECT_DATA=(SID = sidbbdd)) $1 --> jdbc:oracle:thin:@(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)( $2 --> test $3 --> (PORT=1521))(CONNECT_DATA=(SID = sidbbdd))It creates a group.
What is args?
