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Re: [json] json.js breaks for-in loops

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  • Philip Tellis
    ... this is a design flaw in Javascript. You need to check the hasOwnProperty() method when iterating in a for..in loop: for(k in obj)
    Message 1 of 10 , Oct 14, 2006
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      Sometime on Oct 13, PM cobbled together some glyphs to say:

      > By extending the Object.prototype with the new property toJSONString I
      > can no longer use for-in loops in my JavaScript.

      this is a design flaw in Javascript. You need to check the
      hasOwnProperty() method when iterating in a for..in loop:

      for(k in obj)
      if(obj.hasOwnProperty(k))
      foo(k);

      --
      How often I found where I should be going only by setting out for somewhere
      else.
      -- R. Buckminster Fuller
    • Tom Metro
      ... As another poster mentioned, using hasOwnProperty(), is the way to make the intended behavior work. My understanding is that hasOwnProperty() isn t widely
      Message 2 of 10 , Oct 14, 2006
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        Peter Michaux wrote:
        > By extending the Object.prototype with the new property toJSONString I
        > can no longer use for-in loops in my JavaScript.

        As another poster mentioned, using hasOwnProperty(), is the way to make
        the intended behavior work. My understanding is that hasOwnProperty()
        isn't widely supported yet.


        > Has someone released a version of JSON that doesn't do this?

        I thought I remembered seeing a version that had a flag controlling
        whether the methods got added to the stock objects, but clearly that
        isn't in the current version of the code. I think I was thinking of
        another library... It'd be a worthy enhancement for the json.js library.


        > Is it just as simple as changing these
        > Object.prototype.toJSONString = function () {
        >...
        > to something like
        > JSON.objectToJSONString = function () {

        It looks like that should work. The code itself doesn't seem to
        recursively use those method names, instead using s[object type] internally.

        -Tom

        --
        Tom Metro
        Venture Logic, Newton, MA, USA
        "Enterprise solutions through open source."
        Professional Profile: http://tmetro.venturelogic.com/
      • Scott Chapman
        It s easy to modify json.js so it doesn t extend Object.prototype. That was a bad design in my opinion. The version I use is attached. Scott ... [Non-text
        Message 3 of 10 , Oct 14, 2006
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          It's easy to modify json.js so it doesn't extend Object.prototype. That was a
          bad design in my opinion.

          The version I use is attached.

          Scott

          Peter Michaux wrote:
          > Hi,
          >
          > By extending the Object.prototype with the new property toJSONString I
          > can no longer use for-in loops in my JavaScript.
          >
          > Has someone released a version of JSON that doesn't do this?
          >
          > Is it just as simple as changing these
          >
          > Object.prototype.toJSONString = function () {
          > Array.prototype.toJSONString = function () {
          > String.prototype.parseJSON = function () {
          >
          > to something like
          >
          > JSON.objectToJSONString = function () {
          > JSON.arrayToJSONString = function () {
          > JSON.parseJSON = function () {
          >
          > or are their other catches that I have missed?
          >
          > Thank you,
          > Peter



          [Non-text portions of this message have been removed]
        • Martin Cooper
          ... It s not just exceptionally bad design, it s chronically inconsiderate programming. Nobody could use that code inside portlets, because they d risk
          Message 4 of 10 , Oct 14, 2006
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            On 10/14/06, Scott Chapman <scott_list@...> wrote:
            >
            > It's easy to modify json.js so it doesn't extend Object.prototype. That
            > was a
            > bad design in my opinion.


            It's not just exceptionally bad design, it's chronically inconsiderate
            programming. Nobody could use that code inside portlets, because they'd risk
            breaking any and all other JavaScript on the same portal page over which
            they have no control. Even outside a portal environment, it's going to break
            other libraries that developers might already be using, not to mention their
            own code.

            --
            Martin Cooper


            The version I use is attached.
            >
            > Scott
            >
            > Peter Michaux wrote:
            > > Hi,
            > >
            > > By extending the Object.prototype with the new property toJSONString I
            > > can no longer use for-in loops in my JavaScript.
            > >
            > > Has someone released a version of JSON that doesn't do this?
            > >
            > > Is it just as simple as changing these
            > >
            > > Object.prototype.toJSONString = function () {
            > > Array.prototype.toJSONString = function () {
            > > String.prototype.parseJSON = function () {
            > >
            > > to something like
            > >
            > > JSON.objectToJSONString = function () {
            > > JSON.arrayToJSONString = function () {
            > > JSON.parseJSON = function () {
            > >
            > > or are their other catches that I have missed?
            > >
            > > Thank you,
            > > Peter
            >
            >
            >
            > [Non-text portions of this message have been removed]
            >
            >
            >
            >
            > Yahoo! Groups Links
            >
            >
            >
            >
            >
            >


            [Non-text portions of this message have been removed]
          • Stephen M. McKamey
            ... toJSONString I ... make ... A little late to the conversation but... another alternative could be to use the typeof operator (assuming one was iterating
            Message 5 of 10 , Nov 13, 2006
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              --- In json@yahoogroups.com, Tom Metro <tmetro+json@...> wrote:
              >
              > Peter Michaux wrote:
              > > By extending the Object.prototype with the new property
              toJSONString I
              > > can no longer use for-in loops in my JavaScript.
              >
              > As another poster mentioned, using hasOwnProperty(), is the way to
              make
              > the intended behavior work. My understanding is that hasOwnProperty()
              > isn't widely supported yet.

              A little late to the conversation but... another alternative could be
              to use the typeof operator (assuming one was iterating over data):

              for(k in obj)
              if("function"!=typeof obj[k])
              foo(k);

              Thanks,
              smm
            • Martin Cooper
              ... Sure - if the for loop is in your own code, and not some other package that you re just trying to make use of. This issue really needs to be fixed in the
              Message 6 of 10 , Nov 13, 2006
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                On 11/13/06, Stephen M. McKamey <jsonml@...> wrote:
                >
                > --- In json@yahoogroups.com, Tom Metro <tmetro+json@...> wrote:
                > >
                > > Peter Michaux wrote:
                > > > By extending the Object.prototype with the new property
                > toJSONString I
                > > > can no longer use for-in loops in my JavaScript.
                > >
                > > As another poster mentioned, using hasOwnProperty(), is the way to
                > make
                > > the intended behavior work. My understanding is that hasOwnProperty()
                > > isn't widely supported yet.
                >
                > A little late to the conversation but... another alternative could be
                > to use the typeof operator (assuming one was iterating over data):
                >
                > for(k in obj)
                > if("function"!=typeof obj[k])
                > foo(k);


                Sure - if the for loop is in your own code, and not some other package that
                you're just trying to make use of.

                This issue really needs to be fixed in the JSON code, since there's no way
                you can rely on it being fixed in all the other code out there that you
                might want to use.

                --
                Martin Cooper


                Thanks,
                > smm
                >
                >
                >
                >
                >
                > Yahoo! Groups Links
                >
                >
                >
                >
                >


                [Non-text portions of this message have been removed]
              • Stephen M. McKamey
                // This should do what you are asking for while staying // current with Crockford s latest code: // after json.js has loaded... // define a namespace to
                Message 7 of 10 , Nov 13, 2006
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                  // This should do what you are asking for while staying
                  // current with Crockford's latest code:

                  // after json.js has loaded...
                  // define a namespace to minimize footprint
                  var JSON = {};

                  // add all of the methods
                  JSON.arrayToJSONString = Array.prototype.toJSONString;
                  JSON.booleanToJSONString = Boolean.prototype.toJSONString;
                  JSON.dateToJSONString = Date.prototype.toJSONString;
                  JSON.numberToJSONString = Number.prototype.toJSONString;
                  JSON.objectToJSONString = Object.prototype.toJSONString;
                  JSON.stringToJSONString = String.prototype.toJSONString;
                  JSON.parseJSON = String.prototype.parseJSON;

                  // remove all the methods from intrinsic objects
                  delete(Array.prototype.toJSONString);
                  delete(Boolean.prototype.toJSONString);
                  delete(Date.prototype.toJSONString);
                  delete(Number.prototype.toJSONString);
                  delete(Object.prototype.toJSONString);
                  delete(String.prototype.toJSONString);
                  delete(String.prototype.parseJSON);

                  --- In json@yahoogroups.com, "Martin Cooper" <mfncooper@...> wrote:
                  > Sure - if the for loop is in your own code, and not some other
                  package that
                  > you're just trying to make use of.
                  >
                  > This issue really needs to be fixed in the JSON code, since there's
                  no way
                  > you can rely on it being fixed in all the other code out there that
                  you
                  > might want to use.
                • Martin Cooper
                  ... Right. But I don t understand the resistance (or, actually, just lack of any feedback at all) to having the kind of solution I described before (in another
                  Message 8 of 10 , Nov 13, 2006
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                    On 11/13/06, Stephen M. McKamey <jsonml@...> wrote:
                    >
                    > // This should do what you are asking for while staying
                    > // current with Crockford's latest code:


                    Right. But I don't understand the resistance (or, actually, just lack of any
                    feedback at all) to having the kind of solution I described before (in
                    another thread) incorporated into the original source code, so that we don't
                    have to be going and deleting things like that. Here's what I suggested
                    before, which is largely the same as yours, except that mine avoids creation
                    where yours utilises deletion and is necessarily separate (and hence a
                    little less easily maintained) from the original:

                    http://tech.groups.yahoo.com/group/json/message/557

                    --
                    Martin Cooper


                    // after json.js has loaded...
                    > // define a namespace to minimize footprint
                    > var JSON = {};
                    >
                    > // add all of the methods
                    > JSON.arrayToJSONString = Array.prototype.toJSONString;
                    > JSON.booleanToJSONString = Boolean.prototype.toJSONString;
                    > JSON.dateToJSONString = Date.prototype.toJSONString;
                    > JSON.numberToJSONString = Number.prototype.toJSONString;
                    > JSON.objectToJSONString = Object.prototype.toJSONString;
                    > JSON.stringToJSONString = String.prototype.toJSONString;
                    > JSON.parseJSON = String.prototype.parseJSON;
                    >
                    > // remove all the methods from intrinsic objects
                    > delete(Array.prototype.toJSONString);
                    > delete(Boolean.prototype.toJSONString);
                    > delete(Date.prototype.toJSONString);
                    > delete(Number.prototype.toJSONString);
                    > delete(Object.prototype.toJSONString);
                    > delete(String.prototype.toJSONString);
                    > delete(String.prototype.parseJSON);
                    >
                    > --- In json@yahoogroups.com, "Martin Cooper" <mfncooper@...> wrote:
                    > > Sure - if the for loop is in your own code, and not some other
                    > package that
                    > > you're just trying to make use of.
                    > >
                    > > This issue really needs to be fixed in the JSON code, since there's
                    > no way
                    > > you can rely on it being fixed in all the other code out there that
                    > you
                    > > might want to use.
                    >
                    >
                    >
                    >
                    >
                    >
                    > Yahoo! Groups Links
                    >
                    >
                    >
                    >
                    >


                    [Non-text portions of this message have been removed]
                  • Douglas Crockford
                    JavaScript is an imperfect language. The weird interaction between augmentation of prototypes with the for..in statement is evidence of this. This defect in
                    Message 9 of 10 , Nov 14, 2006
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                      JavaScript is an imperfect language. The weird interaction between
                      augmentation of prototypes with the for..in statement is evidence of
                      this. This defect in the language requires that for..in blocks
                      explicitly filter out unwanted stuff that is dredged up from the
                      prototype chain. See http://yuiblog.com/blog/2006/09/26/for-in-intrigue/

                      json.js provides the same API that will be built into ECMAScript
                      Fourth Edition. That means that if your program works with json.js,
                      then it will work even better when the language is revised.

                      Some people do not have the luxury of being forward looking. They have
                      to work with bad code that does not filter for..in, or they claim the
                      right to write bad code themselves. Those people should not be using
                      json.js. Fortunately, JSON encoding and decoding is so easy, there
                      isn't much effort required to make an implementation that works with
                      bad code.

                      JSON is a standard data representation. The json.js implementation is
                      not the standard. It is a reference implementation. You are free to
                      use it in any way that you want, or to not use it.
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