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Re: [json] Helpless beginner

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  • Martin Cooper
    On Thu, May 19, 2011 at 6:47 AM, jonerlandmadsen ... I think perhaps your problem is not a JSON problem per se, which may be why you re having some trouble
    Message 1 of 8 , May 19 7:16 AM
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      On Thu, May 19, 2011 at 6:47 AM, jonerlandmadsen
      <jon.erland.madsen@...> wrote:
      >
      > Hi!
      >
      > I am trying to get an answer to what must be JSON-question number two, but apparently, the answer to my question is too obvious to be included in the Q&As I've found.
      >
      > I will use an external JSON-array in my javascript. It originates from our own server, so there are no security concerns.
      >
      > The address is be for instance:
      >
      > http://www.mysite.no/services/product/list/
      >
      > According to Wikipedia, I can make an object out of it, using "eval". The example given is:
      >
      >
      > var p = eval("(" + contact + ")");
      >
      >
      > ..where 'contact' is the json array contained in a text object.
      >
      > But there must be a step between, that is not explained. The
      > aforementioned external json array has no name. It just starts with a paranthesis [
      >
      > I would thus have to convert it into a string first. How do I do that (javascript does not allow you to read external files into a string, as for instance php does).
      >

      I think perhaps your problem is not a JSON problem per se, which may
      be why you're having some trouble finding the answer. If your server
      is producing a JSON array, that is your string right there. So the
      question really is, how are you calling your server to get that
      string?

      How you do that depends on your client environment. If you're running
      in a browser, you'll want to make an Ajax call. If you're using a
      framework, it will have support for that, so check your framework
      docs. If you're not using a framework, you'll want to work with the
      XMLHttpRequest object. If you're running on the server - for example,
      in Node.js - you'll want to make an HTTP request to your server to get
      the JSON string.

      Once you have the string from your server, you can eval() it, or,
      better, JSON.parse() it, to get your array.

      Hope that helps.

      --
      Martin Cooper


      > Can I convert a json array directly using the url as an argument in eval() (probably not)?
      >
      > I have programmed for 20 years (!) but never used JSON. I feel like a
      > complete fool. I've searched the internet two hours for the answer to
      > this. Even googling json+dummies or json+newbie didn't help. They all write about different parsers.
      >
      > If you could help me, I would be very grateful.
      >
      >
      >
      >
      >
      >
      >
      >
      >
      > ------------------------------------
      >
      > Yahoo! Groups Links
      >
      >
      >
      >
    • Stephan Beal
      On Thu, May 19, 2011 at 3:47 PM, jonerlandmadsen
      Message 2 of 8 , May 19 7:31 AM
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        On Thu, May 19, 2011 at 3:47 PM, jonerlandmadsen <
        jon.erland.madsen@...> wrote:

        > According to Wikipedia, I can make an object out of it, using "eval". The
        > example given is:
        >
        > var p = eval("(" + contact + ")");
        >
        > ..where 'contact' is the json array contained in a text object.
        >
        > But there must be a step between, that is not explained.
        >

        Nope. JSON is a subset of JavaScript and eval() runs the JavaScript which is
        passed to it. The extra parenthesis are a workaround (for what, exactly, i
        don't remember).


        > The
        > aforementioned external json array has no name. It just starts with a
        > paranthesis [
        >

        After the above line runs, it has the name 'p' (the name you gave it).

        --
        ----- stephan beal
        http://wanderinghorse.net/home/stephan/


        [Non-text portions of this message have been removed]
      • jonerlandmadsen
        ... Thank you for your kind answer, but it does not address my problem: How to get the external json array into a text string (that can then be parsed).
        Message 3 of 8 , May 19 7:41 AM
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          --- In json@yahoogroups.com, Stephan Beal <sgbeal@...> wrote:
          >
          > On Thu, May 19, 2011 at 3:47 PM, jonerlandmadsen <
          > jon.erland.madsen@...> wrote:
          >
          > > According to Wikipedia, I can make an object out of it, using "eval". The
          > > example given is:
          > >
          > > var p = eval("(" + contact + ")");
          > >
          > > ..where 'contact' is the json array contained in a text object.
          > >
          > > But there must be a step between, that is not explained.
          > >
          >
          > Nope. JSON is a subset of JavaScript and eval() runs the JavaScript which is
          > passed to it. The extra parenthesis are a workaround (for what, exactly, i
          > don't remember).
          >
          >
          > > The
          > > aforementioned external json array has no name. It just starts with a
          > > paranthesis [
          > >
          >
          > After the above line runs, it has the name 'p' (the name you gave it).
          >
          > --
          > ----- stephan beal
          > http://wanderinghorse.net/home/stephan/
          >
          >
          > [Non-text portions of this message have been removed]
          >

          Thank you for your kind answer, but it does not address my problem: How to get the external json array into a text string (that can then be parsed).
        • Stephan Beal
          On Thu, May 19, 2011 at 4:41 PM, jonerlandmadsen
          Message 4 of 8 , May 19 8:12 AM
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            On Thu, May 19, 2011 at 4:41 PM, jonerlandmadsen <
            jon.erland.madsen@...> wrote:

            > Thank you for your kind answer, but it does not address my problem: How to
            > get the external json array into a text string (that can then be parsed).
            >

            You already have it: the "contact" string is the array, as a JSON-formatted
            string.


            --
            ----- stephan beal
            http://wanderinghorse.net/home/stephan/


            [Non-text portions of this message have been removed]
          • Connie Clark
            Here are several patterns I often use which may help you *If the list data is available at the time your server is returning the rest of the page content *
            Message 5 of 8 , May 19 9:00 AM
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              Here are several patterns I often use which may help you

              *If the list data is available at the time your server is
              returning the rest of the page content
              *
              Pattern.1:

              Have the server emit a script tag that pulls in
              your javascript code for doing something with the list,
              say a function called handleMyList.

              Have the server then emit (within script tags)
              handleMyList( [ item1, item2, item2 ] );


              Pattern.2:

              Have the server emit (within script tags)
              var listArr = [ item1, item2, item3 ];

              Then have the server emit a script tag that
              pulls in your javascript code for doing something
              with listArr.



              *If you need to request the list after the user has
              done other selections:*

              This is quite similar to Pattern.1, but you
              would use an AJAX style request to get the
              content back.

              *OR, to do it "by hand"*

              On your HTML page
              define an iframe IFR
              define a form F
              with action: serverUrl
              target: IFR
              and hidden fields for any parameters
              you need to pass

              When the user makes their selection
              F.parm1.value = "..."
              F.submit();

              Have the server return (within script tags)
              parent.top.handleMyList( [ item1, item2, item3 ]);

              Connie


              On Thu, May 19, 2011 at 6:47 AM, jonerlandmadsen <
              jon.erland.madsen@...> wrote:

              >
              > Hi!
              >
              > I am trying to get an answer to what must be JSON-question number two, but
              > apparently, the answer to my question is too obvious to be included in the
              > Q&As I've found.
              >
              > I will use an external JSON-array in my javascript. It originates from our
              > own server, so there are no security concerns.
              >
              > The address is be for instance:
              >
              > http://www.mysite.no/services/product/list/
              >
              > According to Wikipedia, I can make an object out of it, using "eval". The
              > example given is:
              >
              >
              > var p = eval("(" + contact + ")");
              >
              >
              > ..where 'contact' is the json array contained in a text object.
              >
              > But there must be a step between, that is not explained. The
              > aforementioned external json array has no name. It just starts with a
              > paranthesis [
              >
              > I would thus have to convert it into a string first. How do I do that
              > (javascript does not allow you to read external files into a string, as for
              > instance php does).
              >
              > Can I convert a json array directly using the url as an argument in eval()
              > (probably not)?
              >
              > I have programmed for 20 years (!) but never used JSON. I feel like a
              > complete fool. I've searched the internet two hours for the answer to
              > this. Even googling json+dummies or json+newbie didn't help. They all write
              > about different parsers.
              >
              > If you could help me, I would be very grateful.
              >
              >
              >
              >
              >
              >
              >
              >
              >
              > ------------------------------------
              >
              > Yahoo! Groups Links
              >
              >
              >
              >


              [Non-text portions of this message have been removed]
            • jon.erland.madsen@jiffymade.no
              Thank you so very much! I got help and will use the following code (my script is client side): ********************************************** function
              Message 6 of 8 , May 19 9:57 AM
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                Thank you so very much!

                I got help and will use the following code (my script is client side):

                **********************************************

                function createXMLHttpRequest()
                {
                try { return new XMLHttpRequest(); } catch(e) {}
                try { return new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) {}
                return null;
                }

                var url = "http://www.finansportalen.no/services/sph/produkt/list/";
                var xhReq = createXMLHttpRequest();
                xhReq.open("GET", url, false);
                xhReq.send(null);

                var sphdata = eval(xhReq.responseText);

                **********************************************

                (I would have prefered, however, to have the object declared by the server
                and posted as a .js file i could simply include, thus enabling me to
                access it directly. But the above will do.)

                Thanks again!





                Here are several patterns I often use which may help you

                *If the list data is available at the time your server is
                returning the rest of the page content
                *
                Pattern.1:

                Have the server emit a script tag that pulls in
                your javascript code for doing something with the list,
                say a function called handleMyList.

                Have the server then emit (within script tags)
                handleMyList( [ item1, item2, item2 ] );


                Pattern.2:

                Have the server emit (within script tags)
                var listArr = [ item1, item2, item3 ];

                Then have the server emit a script tag that
                pulls in your javascript code for doing something
                with listArr.



                *If you need to request the list after the user has
                done other selections:*

                This is quite similar to Pattern.1, but you
                would use an AJAX style request to get the
                content back.

                *OR, to do it "by hand"*

                On your HTML page
                define an iframe IFR
                define a form F
                with action: serverUrl
                target: IFR
                and hidden fields for any parameters
                you need to pass

                When the user makes their selection
                F.parm1.value = "..."
                F.submit();

                Have the server return (within script tags)
                parent.top.handleMyList( [ item1, item2, item3 ]);

                Connie


                On Thu, May 19, 2011 at 6:47 AM, jonerlandmadsen <
                jon.erland.madsen@...> wrote:

                >
                > Hi!
                >
                > I am trying to get an answer to what must be JSON-question number two,
                > but
                > apparently, the answer to my question is too obvious to be included in
                > the
                > Q&As I've found.
                >
                > I will use an external JSON-array in my javascript. It originates from
                > our
                > own server, so there are no security concerns.
                >
                > The address is be for instance:
                >
                > http://www.mysite.no/services/product/list/
                >
                > According to Wikipedia, I can make an object out of it, using "eval".
                > The
                > example given is:
                >
                >
                > var p = eval("(" + contact + ")");
                >
                >
                > ..where 'contact' is the json array contained in a text object.
                >
                > But there must be a step between, that is not explained. The
                > aforementioned external json array has no name. It just starts with a
                > paranthesis [
                >
                > I would thus have to convert it into a string first. How do I do that
                > (javascript does not allow you to read external files into a string, as
                > for
                > instance php does).
                >
                > Can I convert a json array directly using the url as an argument in
                > eval()
                > (probably not)?
                >
                > I have programmed for 20 years (!) but never used JSON. I feel like a
                > complete fool. I've searched the internet two hours for the answer to
                > this. Even googling json+dummies or json+newbie didn't help. They all
                > write
                > about different parsers.
                >
                > If you could help me, I would be very grateful.
                >
                >
                >
                >
                >
                >
                >
                >
                >
                > ------------------------------------
                >
                > Yahoo! Groups Links
                >
                >
                >
                >


                [Non-text portions of this message have been removed]
              • kylealanhale
                I want to clarify a couple of things that no one else seems to have addressed: * There is no such thing as an external JSON-array ; JSON is just a data
                Message 7 of 8 , May 20 8:07 AM
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                  I want to clarify a couple of things that no one else seems to have
                  addressed:
                  * There is no such thing as "an external JSON-array"; JSON is just a
                  data transfer format, or, more correctly, a data transfer notation
                  (JavaScript Object Notation). What you described in your last post, of
                  defining the array in a javascript file that you include in your page,
                  is not JSON at all, just JavaScript.
                  * You should never transfer JSON-encoded data as an array; this opens a
                  security vulnerability (see
                  http://directwebremoting.org/blog/joe/2007/03/05/json_is_not_as_safe_as_\
                  people_think_it_is.html for a good summary of the issue); instead,
                  always enclose it in an object. So instead of your data looking like
                  [{"key1": "value1"}, {"key2": "value2"}...], make it look like {"list":
                  [{"key1": "value1"}, {"key2": "value2"}...]}.
                  * You should also never use eval(), for reasons that have been explained
                  extensively elsewhere, including several times by the brainfather of
                  JSON himself, and in the very Wikipedia article you quoted from
                  originally <http://en.wikipedia.org/wiki/JSON#Security_issues>. Instead
                  use JSON.parse, which is standard in all major browsers now.
                  * If you want to get a JavaScript object from a JSON-encoded source
                  while working from the browser, you will invariably use XHR (AJAX, if
                  you must). The method you posted is exactly how you would do that, with
                  the exception that you'd probably want to do it asynchronously and
                  handle the data in a callback, rather than procedurally. Also, if you
                  use a JavaScript framework, it will generally make your life much easier
                  and your code much cleaner. A jQuery example:
                  $.getJSON('http://www.mysite.no/services/product/list/', function(data)
                  { $.each(data.list, function (index, listItem) { // Do something
                  which each item in the list });});
                  Note that this function takes care of (safely) decoding your
                  JSON-encoded data so that you can handle it as a native JavaScript
                  object. See http://api.jquery.com/jQuery.getJSON/ and
                  http://api.jquery.com/jQuery.ajax/ for more details.
                  * While there are exceptions to all of these, and things I have left
                  out, this is a good starting place for best-practices, I think.


                  --- In json@yahoogroups.com, jon.erland.madsen@... wrote:
                  >
                  > Thank you so very much!
                  >
                  > I got help and will use the following code (my script is client side):
                  >
                  > **********************************************
                  >
                  > function createXMLHttpRequest()
                  > {
                  > try { return new XMLHttpRequest(); } catch(e) {}
                  > try { return new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) {}
                  > return null;
                  > }
                  >
                  > var url = "http://www.finansportalen.no/services/sph/produkt/list/";
                  > var xhReq = createXMLHttpRequest();
                  > xhReq.open("GET", url, false);
                  > xhReq.send(null);
                  >
                  > var sphdata = eval(xhReq.responseText);
                  >
                  > **********************************************
                  >
                  > (I would have prefered, however, to have the object declared by the
                  server
                  > and posted as a .js file i could simply include, thus enabling me to
                  > access it directly. But the above will do.)
                  >
                  > Thanks again!
                  >



                  [Non-text portions of this message have been removed]
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