Logging compatible with js

lib/pure/logging.nim

@@ -47,7 +47,9 @@
 ## **Warning:** The global list of handlers is a thread var, this means that
 ## the handlers must be re-added in each thread.
 
-import strutils, os, times
+import strutils, times
+when not defined(js):
+  import os
 
 type
   Level* = enum  ## logging level
@@ -77,6 +79,8 @@ type
   ConsoleLogger* = ref object of Logger ## logger that writes the messages to the
                                         ## console
 
+when not defined(js):
+  type
     FileLogger* = ref object of Logger ## logger that writes the messages to a file
       file*: File  ## the wrapped file.
 
@@ -90,8 +94,9 @@ type
       logFiles: int # how many log files already created, e.g. basename.1, basename.2...
       bufSize: int # size of output buffer (-1: use system defaults, 0: unbuffered, >0: fixed buffer size)
 
-{.deprecated: [TLevel: Level, PLogger: Logger, PConsoleLogger: ConsoleLogger,
+  {.deprecated: [PFileLogger: FileLogger, PRollingFileLogger: RollingFileLogger].}
-    PFileLogger: FileLogger, PRollingFileLogger: RollingFileLogger].}
+
+{.deprecated: [TLevel: Level, PLogger: Logger, PConsoleLogger: ConsoleLogger].}
 
 var
   level {.threadvar.}: Level   ## global log filter
@@ -112,7 +117,7 @@ proc substituteLog*(frmt: string, level: Level, args: varargs[string, `$`]): str
     else:
       inc(i)
       var v = ""
-      var app = getAppFilename()
+      let app = when defined(js): "" else: getAppFilename()
       while frmt[i] in IdentChars:
         v.add(toLower(frmt[i]))
         inc(i)
@@ -121,8 +126,10 @@ proc substituteLog*(frmt: string, level: Level, args: varargs[string, `$`]): str
       of "time": result.add(getClockStr())
       of "datetime": result.add(getDateStr() & "T" & getClockStr())
       of "app":  result.add(app)
-      of "appdir": result.add(app.splitFile.dir)
+      of "appdir":
-      of "appname": result.add(app.splitFile.name)
+        when not defined(js): result.add(app.splitFile.dir)
+      of "appname":
+        when not defined(js): result.add(app.splitFile.name)
       of "levelid": result.add(LevelNames[level][0])
       of "levelname": result.add(LevelNames[level])
       else: discard
@@ -139,9 +146,21 @@ method log*(logger: Logger, level: Level, args: varargs[string, `$`]) {.
 method log*(logger: ConsoleLogger, level: Level, args: varargs[string, `$`]) =
   ## Logs to the console using ``logger`` only.
   if level >= logging.level and level >= logger.levelThreshold:
-    writeLine(stdout, substituteLog(logger.fmtStr, level, args))
+    let ln = substituteLog(logger.fmtStr, level, args)
+    when defined(js):
+      let cln: cstring = ln
+      {.emit: "console.log(`cln`);".}
+    else:
+      writeLine(stdout, ln)
       if level in {lvlError, lvlFatal}: flushFile(stdout)
 
+proc newConsoleLogger*(levelThreshold = lvlAll, fmtStr = defaultFmtStr): ConsoleLogger =
+  ## Creates a new console logger. This logger logs to the console.
+  new result
+  result.fmtStr = fmtStr
+  result.levelThreshold = levelThreshold
+
+when not defined(js):
   method log*(logger: FileLogger, level: Level, args: varargs[string, `$`]) =
     ## Logs to a file using ``logger`` only.
     if level >= logging.level and level >= logger.levelThreshold:
@@ -153,12 +172,6 @@ proc defaultFilename*(): string =
     var (path, name, _) = splitFile(getAppFilename())
     result = changeFileExt(path / name, "log")
 
-proc newConsoleLogger*(levelThreshold = lvlAll, fmtStr = defaultFmtStr): ConsoleLogger =
-  ## Creates a new console logger. This logger logs to the console.
-  new result
-  result.fmtStr = fmtStr
-  result.levelThreshold = levelThreshold
-
   proc newFileLogger*(filename = defaultFilename(),
                       mode: FileMode = fmAppend,
                       levelThreshold = lvlAll,