From 85c41a1398b35c7a0dc1e8d0b0bbcede1f5c3862 Mon Sep 17 00:00:00 2001
From: nigredo-tori <nigredo.tori@gmail.com>
Date: Fri, 20 May 2016 12:17:57 +0600
Subject: [PATCH] Fix toJSStr for control characters

fixes #4190
Add leading zero to encoded character if it is less than 0x10
---
 lib/system/jssys.nim     | 6 +++++-
 tests/js/testtojsstr.nim | 6 ++++++
 2 files changed, 11 insertions(+), 1 deletion(-)
 create mode 100644 tests/js/testtojsstr.nim

diff --git a/lib/system/jssys.nim b/lib/system/jssys.nim
index 99997efe62..ce67373bcf 100644
--- a/lib/system/jssys.nim
+++ b/lib/system/jssys.nim
@@ -248,8 +248,12 @@ proc toJSStr(s: string): cstring {.asmNoStackFrame, compilerproc.} =
     for (var i = 0; i < len; ++i) {
       if (nonAsciiPart !== null) {
         var offset = (i - nonAsciiOffset) * 2;
+        var code = `s`[i].toString(16);
+        if (code.length == 1) {
+          code = "0"+code;
+        }
         nonAsciiPart[offset] = "%";
-        nonAsciiPart[offset + 1] = `s`[i].toString(16);
+        nonAsciiPart[offset + 1] = code;
       }
       else if (`s`[i] < 128)
         asciiPart[i] = fcc(`s`[i]);
diff --git a/tests/js/testtojsstr.nim b/tests/js/testtojsstr.nim
new file mode 100644
index 0000000000..c73b802541
--- /dev/null
+++ b/tests/js/testtojsstr.nim
@@ -0,0 +1,6 @@
+discard """
+  output = ""
+"""
+
+let s: string = "И\n"
+let cs = s.cstring