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RE: [jslint] Collision between global var and function name

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  • Rob Richardson
    It seems effective to identify if a variable is defined as a function (either var f = function () {... or function f() {...) or not and whine if it switches or
    Message 1 of 6 , Sep 9, 2010
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      It seems effective to identify if a variable is defined as a function
      (either var f = function () {... or function f() {...) or not and whine if
      it switches or a function var get set to null. Or perhaps insure that
      variables inside a function don't match the function name. I realize
      there's no classical "types", but it seems to me that a function which
      within itself sets itself to null is doing bad things. Is it practical to
      do this within jslint?

      The corollary to this is name variables more descriptively such that a typo
      won't make it from one valid var to another.

      Rob
    • Cheney, Edward A SSG RES USAR
      Rob, What is the problem if a function changes its method of definition? I do understand that there is a difference between the method of declaring a function
      Message 2 of 6 , Sep 10, 2010
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        Rob,

        What is the problem if a function changes its method of definition? I do understand that there is a difference between the method of declaring a function with regard to execution versus where the function is defined during procedural interpretation of the code at the interpreter, but what problems can you describe where a function morphs during a given scope? JSLint already complains if a single variable name is defined more than once in a given scope. Are you suggestion it would be helpful for JSLint to always prefer one single format for declaring a function? JSLint does not perform flow control and so it cannot know if there exists some sort of poly morphism in your code, by where a function dynamically changes form.

        What is the problem if a function returns null? I understand that a bug is thrown in a function returns null and is executed as part of a mathematical operation or string concatenation. You can prevent this easily enough by ensuring your functions always return a value or an empty string. JSLint does not perform flow control and so no matter how grave a problem this may be it is best fixed proactively and not from validation.

        There is no problem with a variable matching the name of its containing function, because of a difference in namespaces. The problem that arises is if the variable in question is not declared within the function, such as a closure, because then there exists the possibility of a namespace collision. JSLint warns about declarations that cause collisions, but you are on your own for collisions that are the result of reassignment.

        " I realize there's no classical "types", but it seems to me that a function which within itself sets itself to null is doing bad things."
        Not necessarily. A function does not return a value unless it is told to do so. That is not a bad thing, because not all functions are written to return values. Some functions may act to alter the value of closures and other may act to perform operations or extend prototypes. In these cases the functions are merely containers of code that are available for reuse, but do not return values.

        I promise that I am not trying to be a stickler or a pain. I am just trying to pry some specifics out of you because mentioned several things quickly of which each are open to interpretation.

        "The corollary to this is name variables more descriptively such that a typo won't make it from one valid var to another."
        As I discovered early this spring even well named variables can result in unintended collisions between nested operations provided enough reuse and inadequate scope definitions upon where those names are reused. This is part of the nature of extended complexity that comes with Lambda programming.

        Thanks,
        Austin
      • Rob Richardson
        I think I wasn t adequately clear previously. If a variable whose value is a function changes value to a non-function such as number or string or object, I
        Message 3 of 6 , Sep 10, 2010
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          I think I wasn't adequately clear previously. If a variable whose value is
          a function changes value to a non-function such as number or string or
          object, I see this as a concern. The return value of executing the function
          is correctly irrelevant. My question was given the JSLint codebase, is
          adding such a check practical?

          For example, I'd love if JSLint flagged that all these cases were invalid:

          Case 1:

          var somefunc1 = function () {
          somefunc1 = 1; // or null or {} or etc
          };

          Case 2:

          function somefunc2() {
          somefunc2 = 1; // or null or {} or etc
          };

          Case 3:

          someobj.somefunc3 = function () {
          delete someobj.somefunc3;
          };


          ... and aren't lambdas such wonderfully painful and exhilarating things.
          Not since pointer arithmetic could we get so cleaver in such elegant and
          dangerous ways. ("Is this an array of pointers or a pointer to an array?")
          I so love my career.

          Rob


          -----Original Message-----
          From: jslint_com@yahoogroups.com [mailto:jslint_com@yahoogroups.com] On
          Behalf Of Cheney, Edward A SSG RES USAR
          Sent: Friday, September 10, 2010 10:56 AM
          To: jslint_com@yahoogroups.com
          Subject: Re: RE: [jslint] Collision between global var and function name

          Rob,

          What is the problem if a function changes its method of definition? I do
          understand that there is a difference between the method of declaring a
          function with regard to execution versus where the function is defined
          during procedural interpretation of the code at the interpreter, but what
          problems can you describe where a function morphs during a given scope?
          JSLint already complains if a single variable name is defined more than once
          in a given scope. Are you suggestion it would be helpful for JSLint to
          always prefer one single format for declaring a function? JSLint does not
          perform flow control and so it cannot know if there exists some sort of poly
          morphism in your code, by where a function dynamically changes form.

          What is the problem if a function returns null? I understand that a bug is
          thrown in a function returns null and is executed as part of a mathematical
          operation or string concatenation. You can prevent this easily enough by
          ensuring your functions always return a value or an empty string. JSLint
          does not perform flow control and so no matter how grave a problem this may
          be it is best fixed proactively and not from validation.

          There is no problem with a variable matching the name of its containing
          function, because of a difference in namespaces. The problem that arises is
          if the variable in question is not declared within the function, such as a
          closure, because then there exists the possibility of a namespace collision.
          JSLint warns about declarations that cause collisions, but you are on your
          own for collisions that are the result of reassignment.

          " I realize there's no classical "types", but it seems to me that a function
          which within itself sets itself to null is doing bad things."
          Not necessarily. A function does not return a value unless it is told to do
          so. That is not a bad thing, because not all functions are written to
          return values. Some functions may act to alter the value of closures and
          other may act to perform operations or extend prototypes. In these cases
          the functions are merely containers of code that are available for reuse,
          but do not return values.

          I promise that I am not trying to be a stickler or a pain. I am just trying
          to pry some specifics out of you because mentioned several things quickly of
          which each are open to interpretation.

          "The corollary to this is name variables more descriptively such that a typo
          won't make it from one valid var to another."
          As I discovered early this spring even well named variables can result in
          unintended collisions between nested operations provided enough reuse and
          inadequate scope definitions upon where those names are reused. This is
          part of the nature of extended complexity that comes with Lambda
          programming.

          Thanks,
          Austin
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