Interactive Mode for JavaScript.NET

Ever since I read Don's post the other day pointing out the often-overlooked support for a powerful command-line scripting languge in Windows (Javascript), I've been meaning to post this. It's a batch file that will let you run JScript.NET files interactively. Since Javascript is a compiled language, it does this by compiling it to a temporary directory first and then running the compiled EXE. While this might sound slow, as it turns out it's quite acceptable for quick, scripting-type tasks, and it gives me what I've always wanted: a convenient scripting language with full, natural-sytnax access both to COM and the .NET libraries.

Much as I'd like to claim credit for the batch file, I can't. It was written by John Elliott (for whom I don't have a URL) and posted to the WinTech Off-Topic List. The only modification I made was to add the /fast- switch to the compile, which turns off “fast mode”. Near as I can tell (not yet being that familiar with JScript.NET), it makes the code somewhat slower, but enables a lot of the more “scripty” features of the language, such as the ability to add methods dynamically to BCL types. Anyway, here's the script. I called mine rjs.cmd, and stuck it in my \bin directory, which is in my path. Then I can launch scripts by simply running “rjs foo.js“.

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@echo OFF

rem ///////////////////////////////////////////////////////////////////////
rem // js-net-script.cmd
rem // ====================================================================
rem //
rem // Compiles and runs a JScript.NET source file.
rem //

goto :INIT

rem ///////////////////////////////////////////////////////////////////////
rem // HELP procedure
rem // ==============
rem //
rem // Display brief help message
rem //

:HELP

 if defined TRACE %TRACE% [proc %0 %*]
 
 echo Compiles and runs a JScript.NET source file as a console application.
 echo.
 echo JS-NET-SCRIPT script [args]
 echo.
 echo   script       Path to the JScript.NET file you wish to compile and run.
 echo   args         Any arguments you wish to pass to the JScript.NET app.
 echo.

goto :EOF

rem ///////////////////////////////////////////////////////////////////////
rem // MAIN procedure
rem //

:MAIN

 if defined TRACE %TRACE% [proc %0 %*]

 rem // make sure our working directory exists.
 rem // this is where our build outputs will be stored temporarily.
 if not exist "%APPDATA%\js-net-script" mkdir "%APPDATA%\js-net-script"

 rem // determine the various path information we'll need to compile
 rem // and run our script.
 set _ScriptPath=%APPDATA%\js-net-script\%~nx1
 set _ExePath=%_ScriptPath%.exe
 set _LogPath=%_ExePath%.log

 rem // copy the script to ensure it is on a local disk.
 copy "%~f1" "%_ScriptPath%" >nul 2>&1
 if errorlevel 1 set ERR=%errorlevel% && goto :ERROR

 rem // compile the script. we use a debug build so that we can
 rem // break into the debugger. we also log the build results to a
 rem // log file, so that we can show them to the user if there is
 rem // a problem.
 %SYSTEMROOT%\Microsoft.NET\Framework\v1.1.4322\jsc.exe /out:"%_ExePath%" /target:exe /debug+ /fast- /nologo "%_ScriptPath%" > "%_LogPath%" 2>&1
 if errorlevel 1 set ERR=%errorlevel% && goto :ERROR

 rem // run the application, passing in arguments.
 "%_ExePath%" %*

 rem // delete the local copy of the script, and all build outputs.
 del /s /q "%_ScriptPath%*" >nul 2>&1

goto :EOF

rem ///////////////////////////////////////////////////////////////////////
rem // INIT procedure
rem //

:INIT

rem @if not "%ECHO%"=="" echo %ECHO%
@if not "%OS%"=="Windows_NT" goto DOSEXIT

rem Set local scope and call MAIN procedure
 
setlocal & pushd & set RET=

 set SCRIPTNAME=%~n0
 set SCRIPTPATH=%~f0
 
 if "%DEBUG%"=="1" (set TRACE=echo) else (set TRACE=rem)
 
 if /i {%1}=={/help} (call :HELP %2) & (goto :HELPEXIT)
 if /i {%1}=={/?} (call :HELP %2) & (goto :HELPEXIT)

 :INIT_MAIN

 set _SAVED_PROMPT=%PROMPT%
 set PROMPT==$g

 call :MAIN %*

 set PROMPT=%_SAVED_PROMPT%

 :HELPEXIT

 popd & endlocal & set RET=%RET%

goto :EOF

rem ///////////////////////////////////////////////////////////////////////
rem // ERROR procedure
rem // ===============
rem //
rem // Abnormal exit. Expects the errorlevel has been stored in %ERR%.
rem //

:ERROR

 if defined TRACE %TRACE% [ERROR! %0 %*]
 
 echo.
 echo WARNING: Script failed with errorlevel: %ERR%
 echo.
 echo   Current directory is:
 echo     %CD%
 echo   Command-line was:
 echo     %CMDCMDLINE%
 echo.

 rem // show the build log. note: we'll show it in the console, but we
 rem // could also popup notepad.exe
 echo Compiler output:
 echo.
 type "%_LogPath%"
 echo.

 rem notepad "%_LogPath%"

 rem // give the user a chance to see the results.
 rem // note: this is not necessary if we open the log file in notepad.
 rem // note: while paused here, you can copy the build outputs from
 rem // the working directory in %APPDATA% to run ildasm, etc.
 pause

 rem // clean up all the build outputs.
 del /s /q "%_ScriptPath%*" >nul 2>&1

goto :EOF

rem ///////////////////////////////////////////////////////////////////////
rem // DOSEXIT
rem // ====================================================================
rem //
rem // These must be the final lines in the script.
rem //

:DOSEXIT

 echo This script requires Windows NT or later.

rem ///////////////////////////////////////////////////////////////////////

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