better tojsstr (#11954)

* JS: rewrote toJSStr
* JS: don't raise exceptions in primitives

lib/system/jssys.nim

@@ -120,7 +120,7 @@ proc unhandledException(e: ref Exception) {.
   add(buf, "]\n")
   when NimStackTrace:
     add(buf, rawWriteStackTrace())
-  let cbuf : cstring = buf
+  let cbuf = cstring(buf)
   framePtr = nil
   {.emit: """
   if (typeof(Error) !== "undefined") {
@@ -228,37 +228,44 @@ proc cstrToNimstr(c: cstring): string {.asmNoStackFrame, compilerproc.} =
   return result;
   """.}
 
-proc toJSStr(s: string): cstring {.asmNoStackFrame, compilerproc.} =
+proc toJSStr(s: string): cstring {.compilerproc.} =
-  asm """
+  proc fromCharCode(c: char): cstring {.importc: "String.fromCharCode".}
-  if (`s` === null) return "";
+  proc join(x: openArray[cstring]; d = cstring""): cstring {.
-  var len = `s`.length;
+    importcpp: "#.join(@)".}
-  var asciiPart = new Array(len);
+  proc decodeURIComponent(x: cstring): cstring {.
-  var fcc = String.fromCharCode;
+    importc: "decodeURIComponent".}
-  var nonAsciiPart = null;
+
-  var nonAsciiOffset = 0;
+  proc toHexString(c: char; d = 16): cstring {.importcpp: "#.toString(@)".}
-  for (var i = 0; i < len; ++i) {
+
-    if (nonAsciiPart !== null) {
+  proc log(x: cstring) {.importc: "console.log".}
-      var offset = (i - nonAsciiOffset) * 2;
+
-      var code = `s`[i].toString(16);
+  var res = newSeq[cstring](s.len)
-      if (code.length == 1) {
+  var i = 0
-        code = "0"+code;
+  var j = 0
-      }
+  while i < s.len:
-      nonAsciiPart[offset] = "%";
+    var c = s[i]
-      nonAsciiPart[offset + 1] = code;
+    if c < '\128':
-    }
+      res[j] = fromCharCode(c)
-    else if (`s`[i] < 128)
+      inc i
-      asciiPart[i] = fcc(`s`[i]);
+    else:
-    else {
+      var helper = newSeq[cstring]()
-      asciiPart.length = i;
+      while true:
-      nonAsciiOffset = i;
+        let code = toHexString(c)
-      nonAsciiPart = new Array((len - i) * 2);
+        if code.len == 1:
-      --i;
+          helper.add cstring"%0"
-    }
+        else:
-  }
+          helper.add cstring"%"
-  asciiPart = asciiPart.join("");
+        helper.add code
-  return (nonAsciiPart === null) ?
+        inc i
-      asciiPart : asciiPart + decodeURIComponent(nonAsciiPart.join(""));
+        if i >= s.len or s[i] < '\128': break
-  """
+        c = s[i]
+      try:
+        res[j] = decodeURIComponent join(helper)
+      except:
+        res[j] = join(helper)
+    inc j
+  setLen(res, j)
+  result = join(res)
 
 proc mnewString(len: int): string {.asmNoStackFrame, compilerproc.} =
   asm """