querystring: improve stringify() performance

PR-URL: https://github.com/nodejs/node/pull/10852
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Claudio Rodriguez <cjrodr@yahoo.com>

1 files changed, 28 insertions, 21 deletions

diff --git a/lib/querystring.js b/lib/querystring.js
index c22c7c998d..2ced10c72d 100644
--- a/lib/querystring.js
+++ b/lib/querystring.js
@@ -100,12 +100,29 @@ function qsUnescape(s, decodeSpaces) {
 }
 
 
-var hexTable = new Array(256);
+const hexTable = [];
 for (var i = 0; i < 256; ++i)
   hexTable[i] = '%' + ((i < 16 ? '0' : '') + i.toString(16)).toUpperCase();
+
+// These characters do not need escaping when generating query strings:
+// ! - . _ ~
+// ' ( ) *
+// digits
+// alpha (uppercase)
+// alpha (lowercase)
+const noEscape = [
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 0 - 15
+  0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 16 - 31
+  0, 1, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 0, 1, 1, 0, // 32 - 47
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, // 48 - 63
+  0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 64 - 79
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 1, // 80 - 95
+  0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, // 96 - 111
+  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 0  // 112 - 127
+];
+// QueryString.escape() replaces encodeURIComponent()
+// http://www.ecma-international.org/ecma-262/5.1/#sec-15.1.3.4
 function qsEscape(str) {
-  // replaces encodeURIComponent
-  // http://www.ecma-international.org/ecma-262/5.1/#sec-15.1.3.4
   if (typeof str !== 'string') {
     if (typeof str === 'object')
       str = String(str);
@@ -118,30 +135,20 @@ function qsEscape(str) {
   for (var i = 0; i < str.length; ++i) {
     var c = str.charCodeAt(i);
 
-    // These characters do not need escaping (in order):
-    // ! - . _ ~
-    // ' ( ) *
-    // digits
-    // alpha (uppercase)
-    // alpha (lowercase)
-    if (c === 0x21 || c === 0x2D || c === 0x2E || c === 0x5F || c === 0x7E ||
-        (c >= 0x27 && c <= 0x2A) ||
-        (c >= 0x30 && c <= 0x39) ||
-        (c >= 0x41 && c <= 0x5A) ||
-        (c >= 0x61 && c <= 0x7A)) {
-      continue;
-    }
-
-    if (i - lastPos > 0)
-      out += str.slice(lastPos, i);
-
-    // Other ASCII characters
+    // ASCII
     if (c < 0x80) {
+      if (noEscape[c] === 1)
+        continue;
+      if (lastPos < i)
+        out += str.slice(lastPos, i);
       lastPos = i + 1;
       out += hexTable[c];
       continue;
     }
 
+    if (lastPos < i)
+      out += str.slice(lastPos, i);
+
     // Multi-byte characters ...
     if (c < 0x800) {
       lastPos = i + 1;