url: improve parsing speed

The url.parse() function now checks whether an escapable character is
in the URL before trying to escape it.

PR-URL: nodejs/node-v0.x-archive#8638
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

lib/url.js

@@ -319,11 +319,13 @@ Url.prototype.parse = function(url, parseQueryString, slashesDenoteHost) {
     // need to be.
     for (var i = 0, l = autoEscape.length; i < l; i++) {
       var ae = autoEscape[i];
-      var esc = encodeURIComponent(ae);
-      if (esc === ae) {
-        esc = escape(ae);
+      if (rest.indexOf(ae) !== -1) {
+        var esc = encodeURIComponent(ae);
+        if (esc === ae) {
+          esc = escape(ae);
+        }
+        rest = rest.split(ae).join(esc);
       }
-      rest = rest.split(ae).join(esc);
     }
   }