golf: Drive loop with RegExp.prototype.exec

package.json

@@ -2,7 +2,7 @@
   "name": "regexparam",
   "version": "1.0.2",
   "repository": "lukeed/regexparam",
-  "description": "A tiny (252B) utility that converts route patterns into RegExp. Limited alternative to `path-to-regexp` 🙇‍",
+  "description": "A tiny (236B) utility that converts route patterns into RegExp. Limited alternative to `path-to-regexp` 🙇‍",
   "module": "dist/regexparam.mjs",
   "main": "dist/regexparam.js",
   "license": "MIT",

readme.md

@@ -1,6 +1,6 @@
 # regexparam [![Build Status](https://travis-ci.org/lukeed/regexparam.svg?branch=master)](https://travis-ci.org/lukeed/regexparam)
 
-> A tiny (252B) utility that converts route patterns into RegExp. Limited alternative to [`path-to-regexp`](https://github.com/pillarjs/path-to-regexp) 🙇
+> A tiny (236B) utility that converts route patterns into RegExp. Limited alternative to [`path-to-regexp`](https://github.com/pillarjs/path-to-regexp) 🙇
 
 With `regexparam`, you may turn a pathing string (eg, `/users/:id`) into a regular expression.
 

src/index.js

@@ -1,18 +1,22 @@
 export default function (str) {
-	var c, o, tmp, keys=[], pattern='', arr=str.split('/');
-	arr[0] || arr.shift();
+	// This captures:
+	//   1. Leading slash, if any (unused... non-capturing group adds bytes).
+	//   2. Key type, if any.
+	//   3. Key name (or constant path component).
+	//   4. Optional flag.
+	var match, keys=[], pattern='', re=/(\/|^)([:*])?([^\/]*?)(\?)?(?=\/|$)/g;
 
-	while (tmp = arr.shift()) {
-		c = tmp[0];
-		if (c === '*') {
+	// An empty input string will match and not update `lastIndex`, leading to
+	// an infinite loop. The default to '/' avoids this.
+	while (match = re.exec(str || '/')) {
+		if (match[2] === '*') {
 			keys.push('wild');
 			pattern += '/(.*)';
-		} else if (c === ':') {
-			o = tmp[tmp.length - 1] === '?'; // optional?
-			keys.push( tmp.substring(1, o ? tmp.length - 1 : tmp.length) );
-			pattern += o ? '(?:/([^/]+?))?' : '/([^/]+?)';
+		} else if (match[2] === ':') {
+			keys.push( match[3] );
+			pattern += match[4] ? '(?:/([^/]+?))?' : '/([^/]+?)';
 		} else {
-			pattern += '/' + tmp;
+			pattern += '/' + match[3];
 		}
 	}