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-rw-r--r--lib/system/jssys.nim446
1 files changed, 222 insertions, 224 deletions
diff --git a/lib/system/jssys.nim b/lib/system/jssys.nim
index 2f3512cfc..5599240fd 100644
--- a/lib/system/jssys.nim
+++ b/lib/system/jssys.nim
@@ -7,7 +7,8 @@
 #    distribution, for details about the copyright.
 #
 
-import system/indexerrors
+include system/indexerrors
+import std/private/miscdollars
 
 proc log*(s: cstring) {.importc: "console.log", varargs, nodecl.}
 
@@ -48,7 +49,7 @@ proc nimCharToStr(x: char): string {.compilerproc.} =
   result[0] = x
 
 proc isNimException(): bool {.asmNoStackFrame.} =
-  asm "return `lastJSError` && `lastJSError`.m_type;"
+  {.emit: "return `lastJSError` && `lastJSError`.m_type;".}
 
 proc getCurrentException*(): ref Exception {.compilerRtl, benign.} =
   if isNimException(): result = cast[ref Exception](lastJSError)
@@ -68,9 +69,16 @@ proc getCurrentExceptionMsg*(): string =
         return $msg
   return ""
 
+proc setCurrentException*(exc: ref Exception) =
+  lastJSError = cast[PJSError](exc)
+
+proc closureIterSetupExc(e: ref Exception) {.compilerproc, inline.} =
+  ## Used to set up exception handling for closure iterators
+  setCurrentException(e)
+
 proc auxWriteStackTrace(f: PCallFrame): string =
   type
-    TempFrame = tuple[procname: cstring, line: int]
+    TempFrame = tuple[procname: cstring, line: int, filename: cstring]
   var
     it = f
     i = 0
@@ -79,6 +87,7 @@ proc auxWriteStackTrace(f: PCallFrame): string =
   while it != nil and i <= high(tempFrames):
     tempFrames[i].procname = it.procname
     tempFrames[i].line = it.line
+    tempFrames[i].filename = it.filename
     inc(i)
     inc(total)
     it = it.prev
@@ -92,10 +101,9 @@ proc auxWriteStackTrace(f: PCallFrame): string =
     add(result, $(total-i))
     add(result, " calls omitted) ...\n")
   for j in countdown(i-1, 0):
+    result.toLocation($tempFrames[j].filename, tempFrames[j].line, 0)
+    add(result, " at ")
     add(result, tempFrames[j].procname)
-    if tempFrames[j].line > 0:
-      add(result, ", line: ")
-      add(result, $tempFrames[j].line)
     add(result, "\n")
 
 proc rawWriteStackTrace(): string =
@@ -104,6 +112,11 @@ proc rawWriteStackTrace(): string =
   else:
     result = "No stack traceback available\n"
 
+proc writeStackTrace() =
+  var trace = rawWriteStackTrace()
+  trace.setLen(trace.len - 1)
+  echo trace
+
 proc getStackTrace*(): string = rawWriteStackTrace()
 proc getStackTrace*(e: ref Exception): string = e.trace
 
@@ -121,7 +134,8 @@ proc unhandledException(e: ref Exception) {.
   when NimStackTrace:
     add(buf, rawWriteStackTrace())
   let cbuf = cstring(buf)
-  framePtr = nil
+  when NimStackTrace:
+    framePtr = nil
   {.emit: """
   if (typeof(Error) !== "undefined") {
     throw new Error(`cbuf`);
@@ -138,35 +152,35 @@ proc raiseException(e: ref Exception, ename: cstring) {.
     unhandledException(e)
   when NimStackTrace:
     e.trace = rawWriteStackTrace()
-  asm "throw `e`;"
+  {.emit: "throw `e`;".}
 
 proc reraiseException() {.compilerproc, asmNoStackFrame.} =
   if lastJSError == nil:
-    raise newException(ReraiseError, "no exception to reraise")
+    raise newException(ReraiseDefect, "no exception to reraise")
   else:
     if excHandler == 0:
       if isNimException():
         unhandledException(cast[ref Exception](lastJSError))
 
-    asm "throw lastJSError;"
+    {.emit: "throw lastJSError;".}
 
 proc raiseOverflow {.exportc: "raiseOverflow", noreturn, compilerproc.} =
-  raise newException(OverflowError, "over- or underflow")
+  raise newException(OverflowDefect, "over- or underflow")
 
 proc raiseDivByZero {.exportc: "raiseDivByZero", noreturn, compilerproc.} =
-  raise newException(DivByZeroError, "division by zero")
+  raise newException(DivByZeroDefect, "division by zero")
 
 proc raiseRangeError() {.compilerproc, noreturn.} =
-  raise newException(RangeError, "value out of range")
+  raise newException(RangeDefect, "value out of range")
 
 proc raiseIndexError(i, a, b: int) {.compilerproc, noreturn.} =
-  raise newException(IndexError, formatErrorIndexBound(int(i), int(a), int(b)))
+  raise newException(IndexDefect, formatErrorIndexBound(int(i), int(a), int(b)))
 
-proc raiseFieldError(f: string) {.compilerproc, noreturn.} =
-  raise newException(FieldError, f)
+proc raiseFieldError2(f: string, discVal: string) {.compilerproc, noreturn.} =
+  raise newException(FieldDefect, formatFieldDefect(f, discVal))
 
 proc setConstr() {.varargs, asmNoStackFrame, compilerproc.} =
-  asm """
+  {.emit: """
     var result = {};
     for (var i = 0; i < arguments.length; ++i) {
       var x = arguments[i];
@@ -179,13 +193,12 @@ proc setConstr() {.varargs, asmNoStackFrame, compilerproc.} =
       }
     }
     return result;
-  """
+  """.}
 
 proc makeNimstrLit(c: cstring): string {.asmNoStackFrame, compilerproc.} =
   {.emit: """
-  var ln = `c`.length;
-  var result = new Array(ln);
-  for (var i = 0; i < ln; ++i) {
+  var result = [];
+  for (var i = 0; i < `c`.length; ++i) {
     result[i] = `c`.charCodeAt(i);
   }
   return result;
@@ -268,62 +281,64 @@ proc toJSStr(s: string): cstring {.compilerproc.} =
   result = join(res)
 
 proc mnewString(len: int): string {.asmNoStackFrame, compilerproc.} =
-  asm """
-    return new Array(`len`);
-  """
+  {.emit: """
+    var result = new Array(`len`);
+    for (var i = 0; i < `len`; i++) {result[i] = 0;}
+    return result;
+  """.}
 
 proc SetCard(a: int): int {.compilerproc, asmNoStackFrame.} =
   # argument type is a fake
-  asm """
+  {.emit: """
     var result = 0;
     for (var elem in `a`) { ++result; }
     return result;
-  """
+  """.}
 
 proc SetEq(a, b: int): bool {.compilerproc, asmNoStackFrame.} =
-  asm """
+  {.emit: """
     for (var elem in `a`) { if (!`b`[elem]) return false; }
     for (var elem in `b`) { if (!`a`[elem]) return false; }
     return true;
-  """
+  """.}
 
 proc SetLe(a, b: int): bool {.compilerproc, asmNoStackFrame.} =
-  asm """
+  {.emit: """
     for (var elem in `a`) { if (!`b`[elem]) return false; }
     return true;
-  """
+  """.}
 
 proc SetLt(a, b: int): bool {.compilerproc.} =
   result = SetLe(a, b) and not SetEq(a, b)
 
 proc SetMul(a, b: int): int {.compilerproc, asmNoStackFrame.} =
-  asm """
+  {.emit: """
     var result = {};
     for (var elem in `a`) {
       if (`b`[elem]) { result[elem] = true; }
     }
     return result;
-  """
+  """.}
 
 proc SetPlus(a, b: int): int {.compilerproc, asmNoStackFrame.} =
-  asm """
+  {.emit: """
     var result = {};
     for (var elem in `a`) { result[elem] = true; }
     for (var elem in `b`) { result[elem] = true; }
     return result;
-  """
+  """.}
 
 proc SetMinus(a, b: int): int {.compilerproc, asmNoStackFrame.} =
-  asm """
+  {.emit: """
     var result = {};
     for (var elem in `a`) {
       if (!`b`[elem]) { result[elem] = true; }
     }
     return result;
-  """
+  """.}
 
 proc cmpStrings(a, b: string): int {.asmNoStackFrame, compilerproc.} =
-  asm """
+  {.emit: """
     if (`a` == `b`) return 0;
     if (!`a`) return -1;
     if (!`b`) return 1;
@@ -332,13 +347,18 @@ proc cmpStrings(a, b: string): int {.asmNoStackFrame, compilerproc.} =
       if (result != 0) return result;
     }
     return `a`.length - `b`.length;
-  """
+  """.}
 
 proc cmp(x, y: string): int =
-  return cmpStrings(x, y)
+  when nimvm:
+    if x == y: result = 0
+    elif x < y: result = -1
+    else: result = 1
+  else:
+    result = cmpStrings(x, y)
 
 proc eqStrings(a, b: string): bool {.asmNoStackFrame, compilerproc.} =
-  asm """
+  {.emit: """
     if (`a` == `b`) return true;
     if (`a` === null && `b`.length == 0) return true;
     if (`b` === null && `a`.length == 0) return true;
@@ -348,29 +368,29 @@ proc eqStrings(a, b: string): bool {.asmNoStackFrame, compilerproc.} =
     for (var i = 0; i < alen; ++i)
       if (`a`[i] != `b`[i]) return false;
     return true;
-  """
+  """.}
 
 when defined(kwin):
   proc rawEcho {.compilerproc, asmNoStackFrame.} =
-    asm """
+    {.emit: """
       var buf = "";
       for (var i = 0; i < arguments.length; ++i) {
         buf += `toJSStr`(arguments[i]);
       }
       print(buf);
-    """
+    """.}
 
 elif not defined(nimOldEcho):
   proc ewriteln(x: cstring) = log(x)
 
   proc rawEcho {.compilerproc, asmNoStackFrame.} =
-    asm """
+    {.emit: """
       var buf = "";
       for (var i = 0; i < arguments.length; ++i) {
         buf += `toJSStr`(arguments[i]);
       }
       console.log(buf);
-    """
+    """.}
 
 else:
   proc ewriteln(x: cstring) =
@@ -397,78 +417,85 @@ else:
     """.}
 
 # Arithmetic:
+proc checkOverflowInt(a: int) {.asmNoStackFrame, compilerproc.} =
+  {.emit: """
+    if (`a` > 2147483647 || `a` < -2147483648) `raiseOverflow`();
+  """.}
+
 proc addInt(a, b: int): int {.asmNoStackFrame, compilerproc.} =
-  asm """
+  {.emit: """
     var result = `a` + `b`;
-    if (result > 2147483647 || result < -2147483648) `raiseOverflow`();
+    `checkOverflowInt`(result);
     return result;
-  """
+  """.}
 
 proc subInt(a, b: int): int {.asmNoStackFrame, compilerproc.} =
-  asm """
+  {.emit: """
     var result = `a` - `b`;
-    if (result > 2147483647 || result < -2147483648) `raiseOverflow`();
+    `checkOverflowInt`(result);
     return result;
-  """
+  """.}
 
 proc mulInt(a, b: int): int {.asmNoStackFrame, compilerproc.} =
-  asm """
+  {.emit: """
     var result = `a` * `b`;
-    if (result > 2147483647 || result < -2147483648) `raiseOverflow`();
+    `checkOverflowInt`(result);
     return result;
-  """
+  """.}
 
 proc divInt(a, b: int): int {.asmNoStackFrame, compilerproc.} =
-  asm """
+  {.emit: """
     if (`b` == 0) `raiseDivByZero`();
     if (`b` == -1 && `a` == 2147483647) `raiseOverflow`();
     return Math.trunc(`a` / `b`);
-  """
+  """.}
 
 proc modInt(a, b: int): int {.asmNoStackFrame, compilerproc.} =
-  asm """
+  {.emit: """
     if (`b` == 0) `raiseDivByZero`();
     if (`b` == -1 && `a` == 2147483647) `raiseOverflow`();
     return Math.trunc(`a` % `b`);
-  """
+  """.}
+
+proc checkOverflowInt64(a: int64) {.asmNoStackFrame, compilerproc.} =
+  {.emit: """
+    if (`a` > 9223372036854775807n || `a` < -9223372036854775808n) `raiseOverflow`();
+  """.}
 
-proc addInt64(a, b: int): int {.asmNoStackFrame, compilerproc.} =
-  asm """
+proc addInt64(a, b: int64): int64 {.asmNoStackFrame, compilerproc.} =
+  {.emit: """
     var result = `a` + `b`;
-    if (result > 9223372036854775807
-    || result < -9223372036854775808) `raiseOverflow`();
+    `checkOverflowInt64`(result);
     return result;
-  """
+  """.}
 
-proc subInt64(a, b: int): int {.asmNoStackFrame, compilerproc.} =
-  asm """
+proc subInt64(a, b: int64): int64 {.asmNoStackFrame, compilerproc.} =
+  {.emit: """
     var result = `a` - `b`;
-    if (result > 9223372036854775807
-    || result < -9223372036854775808) `raiseOverflow`();
+    `checkOverflowInt64`(result);
     return result;
-  """
+  """.}
 
-proc mulInt64(a, b: int): int {.asmNoStackFrame, compilerproc.} =
-  asm """
+proc mulInt64(a, b: int64): int64 {.asmNoStackFrame, compilerproc.} =
+  {.emit: """
     var result = `a` * `b`;
-    if (result > 9223372036854775807
-    || result < -9223372036854775808) `raiseOverflow`();
+    `checkOverflowInt64`(result);
     return result;
-  """
+  """.}
 
-proc divInt64(a, b: int): int {.asmNoStackFrame, compilerproc.} =
-  asm """
-    if (`b` == 0) `raiseDivByZero`();
-    if (`b` == -1 && `a` == 9223372036854775807) `raiseOverflow`();
-    return Math.trunc(`a` / `b`);
-  """
+proc divInt64(a, b: int64): int64 {.asmNoStackFrame, compilerproc.} =
+  {.emit: """
+    if (`b` == 0n) `raiseDivByZero`();
+    if (`b` == -1n && `a` == 9223372036854775807n) `raiseOverflow`();
+    return `a` / `b`;
+  """.}
 
-proc modInt64(a, b: int): int {.asmNoStackFrame, compilerproc.} =
-  asm """
-    if (`b` == 0) `raiseDivByZero`();
-    if (`b` == -1 && `a` == 9223372036854775807) `raiseOverflow`();
-    return Math.trunc(`a` % `b`);
-  """
+proc modInt64(a, b: int64): int64 {.asmNoStackFrame, compilerproc.} =
+  {.emit: """
+    if (`b` == 0n) `raiseDivByZero`();
+    if (`b` == -1n && `a` == 9223372036854775807n) `raiseOverflow`();
+    return `a` % `b`;
+  """.}
 
 proc negInt(a: int): int {.compilerproc.} =
   result = a*(-1)
@@ -482,34 +509,12 @@ proc absInt(a: int): int {.compilerproc.} =
 proc absInt64(a: int64): int64 {.compilerproc.} =
   result = if a < 0: a*(-1) else: a
 
-when not defined(nimNoZeroExtendMagic):
-  proc ze*(a: int): int {.compilerproc.} =
-    result = a
-
-  proc ze64*(a: int64): int64 {.compilerproc.} =
-    result = a
-
-  proc toU8*(a: int): int8 {.asmNoStackFrame, compilerproc.} =
-    asm """
-      return `a`;
-    """
-
-  proc toU16*(a: int): int16 {.asmNoStackFrame, compilerproc.} =
-    asm """
-      return `a`;
-    """
-
-  proc toU32*(a: int64): int32 {.asmNoStackFrame, compilerproc.} =
-    asm """
-      return `a`;
-    """
-
 proc nimMin(a, b: int): int {.compilerproc.} = return if a <= b: a else: b
 proc nimMax(a, b: int): int {.compilerproc.} = return if a >= b: a else: b
 
-proc chckNilDisp(p: pointer) {.compilerproc.} =
+proc chckNilDisp(p: JSRef) {.compilerproc.} =
   if p == nil:
-    sysFatal(NilAccessError, "cannot dispatch; dispatcher is nil")
+    sysFatal(NilAccessDefect, "cannot dispatch; dispatcher is nil")
 
 include "system/hti"
 
@@ -525,22 +530,22 @@ proc nimCopyAux(dest, src: JSRef, n: ptr TNimNode) {.compilerproc.} =
   case n.kind
   of nkNone: sysAssert(false, "nimCopyAux")
   of nkSlot:
-    asm """
+    {.emit: """
       `dest`[`n`.offset] = nimCopy(`dest`[`n`.offset], `src`[`n`.offset], `n`.typ);
-    """
+    """.}
   of nkList:
-    asm """
+    {.emit: """
     for (var i = 0; i < `n`.sons.length; i++) {
       nimCopyAux(`dest`, `src`, `n`.sons[i]);
     }
-    """
+    """.}
   of nkCase:
-    asm """
+    {.emit: """
       `dest`[`n`.offset] = nimCopy(`dest`[`n`.offset], `src`[`n`.offset], `n`.typ);
       for (var i = 0; i < `n`.sons.length; ++i) {
         nimCopyAux(`dest`, `src`, `n`.sons[i][1]);
       }
-    """
+    """.}
 
 proc nimCopy(dest, src: JSRef, ti: PNimType): JSRef =
   case ti.kind
@@ -548,9 +553,9 @@ proc nimCopy(dest, src: JSRef, ti: PNimType): JSRef =
     if not isFatPointer(ti):
       result = src
     else:
-      asm "`result` = [`src`[0], `src`[1]];"
+      {.emit: "`result` = [`src`[0], `src`[1]];".}
   of tySet:
-    asm """
+    {.emit: """
       if (`dest` === null || `dest` === undefined) {
         `dest` = {};
       }
@@ -559,80 +564,72 @@ proc nimCopy(dest, src: JSRef, ti: PNimType): JSRef =
       }
       for (var key in `src`) { `dest`[key] = `src`[key]; }
       `result` = `dest`;
-    """
+    """.}
   of tyTuple, tyObject:
     if ti.base != nil: result = nimCopy(dest, src, ti.base)
     elif ti.kind == tyObject:
-      asm "`result` = (`dest` === null || `dest` === undefined) ? {m_type: `ti`} : `dest`;"
+      {.emit: "`result` = (`dest` === null || `dest` === undefined) ? {m_type: `ti`} : `dest`;".}
     else:
-      asm "`result` = (`dest` === null || `dest` === undefined) ? {} : `dest`;"
+      {.emit: "`result` = (`dest` === null || `dest` === undefined) ? {} : `dest`;".}
     nimCopyAux(result, src, ti.node)
-  of tySequence, tyArrayConstr, tyOpenArray, tyArray:
-    asm """
+  of tyArrayConstr, tyArray:
+    # In order to prevent a type change (TypedArray -> Array) and to have better copying performance,
+    # arrays constructors are considered separately
+    {.emit: """
+      if(ArrayBuffer.isView(`src`)) { 
+        if(`dest` === null || `dest` === undefined || `dest`.length != `src`.length) {
+          `dest` = new `src`.constructor(`src`);
+        } else {
+          `dest`.set(`src`, 0);
+        }
+        `result` = `dest`;
+      } else {
+        if (`src` === null) {
+          `result` = null;
+        }
+        else {
+          if (`dest` === null || `dest` === undefined || `dest`.length != `src`.length) {
+            `dest` = new Array(`src`.length);
+          }
+          `result` = `dest`;
+          for (var i = 0; i < `src`.length; ++i) {
+            `result`[i] = nimCopy(`result`[i], `src`[i], `ti`.base);
+          }
+        }
+      }
+    """.}
+  of tySequence, tyOpenArray:
+    {.emit: """
       if (`src` === null) {
         `result` = null;
       }
       else {
-        if (`dest` === null || `dest` === undefined) {
+        if (`dest` === null || `dest` === undefined || `dest`.length != `src`.length) {
           `dest` = new Array(`src`.length);
         }
-        else {
-          `dest`.length = `src`.length;
-        }
         `result` = `dest`;
         for (var i = 0; i < `src`.length; ++i) {
           `result`[i] = nimCopy(`result`[i], `src`[i], `ti`.base);
         }
       }
-    """
+    """.}
   of tyString:
-    asm """
+    {.emit: """
       if (`src` !== null) {
         `result` = `src`.slice(0);
       }
-    """
+    """.}
   else:
     result = src
 
-proc genericReset(x: JSRef, ti: PNimType): JSRef {.compilerproc.} =
-  asm "`result` = null;"
-  case ti.kind
-  of tyPtr, tyRef, tyVar, tyNil:
-    if isFatPointer(ti):
-      asm """
-        `result` = [null, 0];
-      """
-  of tySet:
-    asm """
-      `result` = {};
-    """
-  of tyTuple, tyObject:
-    if ti.kind == tyObject:
-      asm "`result` = {m_type: `ti`};"
-    else:
-      asm "`result` = {};"
-  of tySequence, tyOpenArray:
-    asm """
-      `result` = [];
-    """
-  of tyArrayConstr, tyArray:
-    asm """
-      `result` = new Array(`x`.length);
-      for (var i = 0; i < `x`.length; ++i) {
-        `result`[i] = genericReset(`x`[i], `ti`.base);
-      }
-    """
-  else:
-    discard
-
 proc arrayConstr(len: int, value: JSRef, typ: PNimType): JSRef {.
                 asmNoStackFrame, compilerproc.} =
   # types are fake
-  asm """
+  {.emit: """
     var result = new Array(`len`);
     for (var i = 0; i < `len`; ++i) result[i] = nimCopy(null, `value`, `typ`);
     return result;
-  """
+  """.}
 
 proc chckIndx(i, a, b: int): int {.compilerproc.} =
   if i >= a and i <= b: return i
@@ -648,7 +645,7 @@ proc chckObj(obj, subclass: PNimType) {.compilerproc.} =
   if x == subclass: return # optimized fast path
   while x != subclass:
     if x == nil:
-      raise newException(ObjectConversionError, "invalid object conversion")
+      raise newException(ObjectConversionDefect, "invalid object conversion")
     x = x.base
 
 proc isObj(obj, subclass: PNimType): bool {.compilerproc.} =
@@ -661,11 +658,12 @@ proc isObj(obj, subclass: PNimType): bool {.compilerproc.} =
   return true
 
 proc addChar(x: string, c: char) {.compilerproc, asmNoStackFrame.} =
-  asm "`x`.push(`c`);"
+  {.emit: "`x`.push(`c`);".}
 
 {.pop.}
 
 proc tenToThePowerOf(b: int): BiggestFloat =
+  # xxx deadcode
   var b = b
   var a = 10.0
   result = 1.0
@@ -679,86 +677,75 @@ proc tenToThePowerOf(b: int): BiggestFloat =
 const
   IdentChars = {'a'..'z', 'A'..'Z', '0'..'9', '_'}
 
-# XXX use JS's native way here
-proc nimParseBiggestFloat(s: string, number: var BiggestFloat, start = 0): int {.
-                          compilerproc.} =
-  var
-    esign = 1.0
-    sign = 1.0
-    i = start
-    exponent: int
-    flags: int
-  number = 0.0
+
+proc parseFloatNative(a: openarray[char]): float =
+  var str = ""
+  for x in a:
+    str.add x
+
+  let cstr = cstring str
+
+  {.emit: """
+  `result` = Number(`cstr`);
+  """.}
+
+proc nimParseBiggestFloat(s: openarray[char], number: var BiggestFloat): int {.compilerproc.} =
+  var sign: bool
+  var i = 0
   if s[i] == '+': inc(i)
   elif s[i] == '-':
-    sign = -1.0
+    sign = true
     inc(i)
   if s[i] == 'N' or s[i] == 'n':
     if s[i+1] == 'A' or s[i+1] == 'a':
       if s[i+2] == 'N' or s[i+2] == 'n':
         if s[i+3] notin IdentChars:
           number = NaN
-          return i+3 - start
+          return i+3
     return 0
   if s[i] == 'I' or s[i] == 'i':
     if s[i+1] == 'N' or s[i+1] == 'n':
       if s[i+2] == 'F' or s[i+2] == 'f':
         if s[i+3] notin IdentChars:
-          number = Inf*sign
-          return i+3 - start
+          number = if sign: -Inf else: Inf
+          return i+3
     return 0
-  while s[i] in {'0'..'9'}:
-    # Read integer part
-    flags = flags or 1
-    number = number * 10.0 + toFloat(ord(s[i]) - ord('0'))
+
+  var buf: string
+    # we could also use an `array[char, N]` buffer to avoid reallocs, or
+    # use a 2-pass algorithm that first computes the length.
+  if sign: buf.add '-'
+  template addInc =
+    buf.add s[i]
     inc(i)
+  template eatUnderscores =
     while s[i] == '_': inc(i)
-  # Decimal?
-  if s[i] == '.':
-    var hd = 1.0
+  while s[i] in {'0'..'9'}: # Read integer part
+    buf.add s[i]
     inc(i)
-    while s[i] in {'0'..'9'}:
-      # Read fractional part
-      flags = flags or 2
-      number = number * 10.0 + toFloat(ord(s[i]) - ord('0'))
-      hd = hd * 10.0
-      inc(i)
-      while s[i] == '_': inc(i)
-    number = number / hd # this complicated way preserves precision
+    eatUnderscores()
+  if s[i] == '.': # Decimal?
+    addInc()
+    while s[i] in {'0'..'9'}: # Read fractional part
+      addInc()
+      eatUnderscores()
   # Again, read integer and fractional part
-  if flags == 0: return 0
-  # Exponent?
-  if s[i] in {'e', 'E'}:
-    inc(i)
-    if s[i] == '+':
-      inc(i)
-    elif s[i] == '-':
-      esign = -1.0
-      inc(i)
-    if s[i] notin {'0'..'9'}:
-      return 0
+  if buf.len == ord(sign): return 0
+  if s[i] in {'e', 'E'}: # Exponent?
+    addInc()
+    if s[i] == '+': inc(i)
+    elif s[i] == '-': addInc()
+    if s[i] notin {'0'..'9'}: return 0
     while s[i] in {'0'..'9'}:
-      exponent = exponent * 10 + ord(s[i]) - ord('0')
-      inc(i)
-      while s[i] == '_': inc(i)
-  # Calculate Exponent
-  let hd = tenToThePowerOf(exponent)
-  if esign > 0.0: number = number * hd
-  else:           number = number / hd
-  # evaluate sign
-  number = number * sign
-  result = i - start
-
-when defined(nodejs):
-  # Deprecated. Use `alert` defined in dom.nim
-  proc alert*(s: cstring) {.importc: "console.log", nodecl, deprecated.}
-else:
-  # Deprecated. Use `alert` defined in dom.nim
-  proc alert*(s: cstring) {.importc, nodecl, deprecated.}
+      addInc()
+      eatUnderscores()
+  number = parseFloatNative(buf)
+  result = i
 
 # Workaround for IE, IE up to version 11 lacks 'Math.trunc'. We produce
 # 'Math.trunc' for Nim's ``div`` and ``mod`` operators:
-const jsMathTrunc = """
+when defined(nimJsMathTruncPolyfill):
+  {.emit: """
 if (!Math.trunc) {
   Math.trunc = function(v) {
     v = +v;
@@ -766,5 +753,16 @@ if (!Math.trunc) {
     return (v - v % 1) || (v < 0 ? -0 : v === 0 ? v : 0);
   };
 }
-"""
-when not defined(nodejs): {.emit: jsMathTrunc .}
+""".}
+
+proc cmpClosures(a, b: JSRef): bool {.compilerproc, asmNoStackFrame.} =
+  # Both `a` and `b` need to be a closure
+  {.emit: """
+    if (`a` !== null && `a`.ClP_0 !== undefined &&
+        `b` !== null && `b`.ClP_0 !== undefined) {
+      return `a`.ClP_0 == `b`.ClP_0 && `a`.ClE_0 == `b`.ClE_0;
+    } else {
+      return `a` == `b`;
+    }
+  """
+  .}