README.md

regexp-preprocessor

Preprocessor to create extended Javascript RegularExpressions.

Adds labelled capturing groups to your regexes.The implementation has the advantage that one can work with native RegExp objects at any time, since the proposed syntax does not contradict the native grammar. The preprocessor compiles your regular expression to an equivalent expression without any labels and returns an extended RegExp object (the basic interface does not change). To access the groups, the resulting match object is enhanced by a group(id) method, which also works for the numeric grouping.

The parser respects non capturing groups and allows arbitrary nesting and combination of labelled and default groups.

#Caveats

• The preprocessing has a high overhead.

##Installation

npm install {name}

##Syntax To add a named group to your regular expression, mark the group with a label embraced by colons (:label:pattern). Labelled and numeric indexed groups can be arbitrarily nested and combined. Consider the following examples:

// e.g. /root/files/Readme.md
/\/root\/files\/(:filename:\w+\.\w+)/

// e.g. /root/files/Readme.md
/\/root\/files\/(:filename:\w+\.(:fileextension:\w+))/

// e.g. /somewhere/files/subfolder/Readme.md
/\/(\w+)\/files\/(\w+)\/(:filename:\w+\.(:fileextension:\w+))/

// e.g. /someRoot/files/subfolder/Readme10.md
/\/(\w+)\/files\/(\w+)\/(:filename:\w+(\d)\.(:fileextension:\w+))/

The replacement syntax works analogous using $:labelname:

var replacement = '$1 is the first capturing group, $:filename: the labelled group';

##Matching Instantiate the preprocessor and pass the Regexp which should be processed.

var Preprocessor = require('{name}');

var   proc = new Preprocessor()
    , extended = proc.preprocess(/regex(:type:\w+)/);

var match = extended.exec('regexSuper');
if(match){
    match.group('type'); // Super
    match.group(1);      // Super
    match[1];            // Super
}

##Replacement The extended RegExps' support replacement of named groups:

extended.replace('regexSuper', 'Regex: $:type:'); // 'Regex: Super'