To explicit RegExp

to-explicit-re.js

/**
 * toExplicitRe
 * Converts implicit concatenations of RegExps into explicit ones
 * by adding dot "." symbol as the concatenation symbol.
 *
 * The explicit format of RegExps is used by https://gist.github.com/1239804
 *
 * Examples:
 *
 *   - abc => a.b.c
 *   - a+bc => a+.b.c
 *   - a(bb)+c => a.(b.b)+.c
 *
 * by Dmitry Soshnikov <[email protected]>
 * MIT Style License
 *
 */
function toExplicitRe(reStr, dontPrint) {
  var explicitRe = reStr.replace(/([a-zA-Z0-9)*+])(?=[a-za-zA-Z0-9(])/g, "$1.");
  !dontPrint && console.log(reStr, "=>", explicitRe);
  return explicitRe;
}

// tests
toExplicitRe("abc"); // a.b.c
toExplicitRe("a+bc"); // a.b.c
toExplicitRe("a(bb)+c"); // a.b.c
toExplicitRe("a|b*c"); // a|b*.c