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3170 :: Too many global variables in a generated js-code

• alexsad (orginal) [2017-09-15T11:07:22+02:00] view original

  After compilation to js and run it in the browser I see in developer tools that window object has many variables. You can also detect them in https://nim-lang.org/docs/theindex.html

  I've heard global variables are bad.

  https://yuiblog.com/blog/2006/06/01/global-domination/

  Is it possible to avoid it?

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• Araq (orginal) [2017-09-15T14:32:53+02:00] view original

  I've heard assembler is very unsafe and low level -- is asm generation possible to avoid with GCC?

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• Tiberium (orginal) [2017-09-15T14:38:41+02:00] view original

  @alexsad - don't try to compare JS code compiled by Nim with hand-written JS. It's almost the same if you compare hand-written C++ with C++ code compiled by Nim

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• alexsad (orginal) [2017-09-15T15:30:43+02:00] view original

  I think the problem will be if we compile two js-files and include them to html. then some global variables will be overwritten.

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• Araq (orginal) [2017-09-15T16:05:02+02:00] view original

  Yeah ok, you can only compile a single Nim program to JS. But that program can consist of as many Nim modules as necessary.

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• HBehrens (orginal) [2017-09-15T19:57:43+02:00] view original

  I am generally wrapping the generated JS code in several steps but essentially, it's:

  
  (function(){
  // generated nim code
  })();
  Run

  This way, most of the assignments in the generated code create variables local to this anonymous function (since there declarations are starting with var). There are a few exceptions, such as

  
  if (typeof Int8Array === 'undefined') Int8Array = Array;
  Run

  But I find that typed arrays are available on the environments I run JS anyway. On Chrome today, the expression

  
  Object.keys(window).length
  Run

  evaluates to 195 (for this forum website) before and after running a minimal echo "Hello, World!" that I cross-compiled to JS and wrapped with the pattern above.

  In my actual project, I am using webpack and a suffix in the form of

  
  exports.funcA ==funcA;
  ...
  Run

  to declare proper CommonJS modules. With that, I get not only proper guards against pollution of the global scope but also benefits such as tree shaking and magnification "for free".

  This is my command in the run section of my package.json

  
      "nim": "nim js -d:release --noMain --lineDir:on --embedsrc --nimCache:src/nim_generated src/nim/game.nim 2>&1 && echo \"exports.init = game_init; exports.update = game_update; exports.render = game_render;\" >>src/nim_generated/game.js",
  Run

  The resulting JS code is pretty compact :)

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• alexsad (orginal) [2017-09-18T07:48:34+02:00] view original

  @Araq - thanks. I like it that from more Nim modules compile along js file. I have known it. I will try to find workround to run two or more js in the same time. Then I will post. ...and sorry for my english.

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• alexsad (orginal) [2017-09-18T10:53:21+02:00] view original

  @HBehrens - thanks a lot! This is very helpful.

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