Browser Check

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  • McKirahan
    #1

    Browser Check

    Is this a very good browser check?

    <html>
    <head>
    <title>wB.htm </title>
    <script type="text/javascript">
    var adBtype = "??";
    function wB() {
    if (document.getEl ementById && !document.all) {
    adBtype = "NS6+";
    } else if (document.getEl ementById && document.all) {
    adBtype = "IE5+";
    } else if (document.all) {
    adBtype = "IE4";
    } else if (document.layer s) {
    adBtype = "NS4";
    }
    alert(adBtype);
    }
    </script>
    </head>
    <body onload="wB()">
    <body>
    </html>

    Opera 6.01 returns "IE5+"; don't know about others...


    Tags: None
    • Andrew Urquhart
      #2
      Re: Browser Check

      "McKirahan" <News@McKirahan .com> wrote in message
      news:Jm9%b.5668 6$Xp.269424@att bi_s54...[color=blue]
      > Is this a very good browser check?[/color]

      <script cut>

      See: http://jibbering.com/faq/#FAQ4_26
      --
      Andrew Urquhart
      - FAQ: http://jibbering.com/faq
      - Archive: http://groups.google.com/groups?grou...ang.javascript
      - Reply: https://www.andrewu.co.uk/about/cont...=newsgroup_clj


        Comment

        • Lasse Reichstein Nielsen
          #3
          Re: Browser Check

          "McKirahan" <News@McKirahan .com> writes:
          [color=blue]
          > Is this a very good browser check?[/color]

          No. I can say that without reading, because browser checks are almost
          invariably not good, no matter how efficient they are :).

          (Remember DOCTYPE, it is required by HTML)
          [color=blue]
          > var adBtype = "??";
          > function wB() {
          > if (document.getEl ementById && !document.all) {
          > adBtype = "NS6+";[/color]

          Or Opera 6 or ....
          [color=blue]
          > } else if (document.getEl ementById && document.all) {
          > adBtype = "IE5+";[/color]

          Or Opera 6 (in IE mode) or Opera 7 or ...
          [color=blue]
          > } else if (document.all) {
          > adBtype = "IE4";[/color]

          Or WebTV or ....
          [color=blue]
          > } else if (document.layer s) {
          > adBtype = "NS4";[/color]

          Or OmniWeb or ...
          [color=blue]
          > Opera 6.01 returns "IE5+"; don't know about others...[/color]

          Not knowing about others is *the* problem with browser detection.
          Optimistically it is hard work to become familiar with all browsers,
          realistically, it is quite impossible. You will invariably miss some
          browsers that are in actual use, and will most likely badly
          misrepresent future browsers.

          The way to make scripts usefull across as many browsers as possible
          are:
          1) Use standards! It gives you the best chance of forward compatability.
          2) Use object/feature detection, not browser detection, to make fallbacks
          for non-standard-compliant browsers.

          Object detection coulde be:

          var elem;
          if (document.getEl ementById) {
          elem = document.getEle mentById(id);
          } else if (document.all) {
          elem = document.all[id];
          } else if (document.layer s) {
          elem = document.layers[id];
          } else {
          elem = null;
          }

          Before using a standard feature that some browsers are known to be
          incompatible with, you test for its existence. If it doesn't exist,
          you test for the existence of some other feature that might (or might
          not) be used instead. Notice that the above code doesn't care whether
          it is IE 5+ or NS 6+ or whatever. It is not perfect code! There are
          cases where it fails too, which further testing could fix. And some
          that it can't (some browsers are just broken, or doesn't have
          Javascript enabled).

          It is important to realize that old browsers that nobody uses will not
          become more used in the future, but future browsers will. That makes
          forward compatability more important than backwards compatability.
          Detecting specific versions of known browsers will necessarily not
          work for future versions.


          /L
          --
          Lasse Reichstein Nielsen - lrn@hotpop.com
          DHTML Death Colors: <URL:http://www.infimum.dk/HTML/rasterTriangleD OM.html>
          'Faith without judgement merely degrades the spirit divine.'

            Comment

            • Mick White
              #4
              Re: Browser Check

              McKirahan wrote:

              [color=blue]
              > <script type="text/javascript">
              > var adBtype = "??";
              > function wB() {
              > if (document.getEl ementById && !document.all) {
              > adBtype = "NS6+";
              > } else if (document.getEl ementById && document.all) {
              > adBtype = "IE5+";
              > } else if (document.all) {
              > adBtype = "IE4";
              > } else if (document.layer s) {
              > adBtype = "NS4";
              > }
              > alert(adBtype);
              > }
              ></script>[/color]

              There's no escape for the function:


              function wB() {
              if (document.getEl ementById && !document.all) {
              adBtype = "NS6+";retu rn;
              }
              if (document.getEl ementById && document.all) {
              adBtype = "IE5+";retu rn;
              }
              if (document.all) {
              adBtype = "IE4";retur n;
              }
              if (document.layer s) {
              adBtype = "NS4";retur n;
              }
              adBtype= "unknown to this programmer";
              }
              Mick

                Comment

                • McKirahan
                  #5
                  Re: Browser Check

                  "Mick White" <mwhite13@BOGUS rochester.rr.co m> wrote in message
                  news:0Fb%b.9200 8$%72.76902@twi ster.nyroc.rr.c om...[color=blue]
                  > McKirahan wrote:
                  >
                  >[color=green]
                  > > <script type="text/javascript">
                  > > var adBtype = "??";
                  > > function wB() {
                  > > if (document.getEl ementById && !document.all) {
                  > > adBtype = "NS6+";
                  > > } else if (document.getEl ementById && document.all) {
                  > > adBtype = "IE5+";
                  > > } else if (document.all) {
                  > > adBtype = "IE4";
                  > > } else if (document.layer s) {
                  > > adBtype = "NS4";
                  > > }
                  > > alert(adBtype);
                  > > }
                  > ></script>[/color]
                  >
                  > There's no escape for the function:
                  >
                  >
                  > function wB() {
                  > if (document.getEl ementById && !document.all) {
                  > adBtype = "NS6+";retu rn;
                  > }
                  > if (document.getEl ementById && document.all) {
                  > adBtype = "IE5+";retu rn;
                  > }
                  > if (document.all) {
                  > adBtype = "IE4";retur n;
                  > }
                  > if (document.layer s) {
                  > adBtype = "NS4";retur n;
                  > }
                  > adBtype= "unknown to this programmer";
                  > }
                  > Mick[/color]

                  Actually I modified one I found; it actually was:

                  function wB() {
                  if (document.getEl ementById && !document.all) {
                  adBtype = "NS6+";
                  return;
                  } else if (document.getEl ementById && document.all) {
                  adBtype = "IE5+";
                  return;
                  } else if (document.all) {
                  adBtype = "IE4";
                  return;
                  } else if (document.layer s) {
                  adBtype = "NS4";
                  return;
                  }
                  }


                    Comment

                    • kaeli
                      #6
                      Re: Browser Check

                      In article <Jm9%b.56686$Xp .269424@attbi_s 54>, News@McKirahan. com
                      enlightened us with...[color=blue]
                      > Is this a very good browser check?[/color]

                      No, but it's a great way of doing object detection. :)

                      There is NO good browser check. There are simply too many browsers.

                      --
                      --
                      ~kaeli~
                      I do whatever my Rice Krispies tell me to.
                      http://www.ipwebdesign.net/wildAtHeart

                      http://www.ipwebdesign.net/kaelisSpace


                        Comment

                        • Mick White
                          #7
                          Re: Browser Check

                          McKirahan wrote:

                          [color=blue]
                          >
                          > Actually I modified one I found; it actually was:
                          >
                          > function wB() {
                          > if (document.getEl ementById && !document.all) {
                          > adBtype = "NS6+";
                          > return;
                          > } else if (document.getEl ementById && document.all) {
                          > adBtype = "IE5+";
                          > return;
                          > } else if (document.all) {
                          > adBtype = "IE4";
                          > return;
                          > } else if (document.layer s) {
                          > adBtype = "NS4";
                          > return;
                          > }
                          > }
                          >[/color]

                          What if all the Booleans are false? You need to declare a global variable:
                          var adBtype="Unknow n" // A suggestion.
                          But read the other comments, there are probably hundreds of different
                          browsers out there, some of which obfuscate their headers. IOW your
                          "adBtype" is just a guess.
                          Mick

                            Comment

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