image precaching

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  • viza
    #1

    image precaching

    Hi!

    This does not seem to work:

    function cacheimage(sour ce){
    myimg=new Image()
    myimg.src=sourc e
    }
    cacheimage('clo sed1.jpg')

    Is this because the myimg object is destroyed as soon as the function
    returns, or for some other reason? Does anyone have a simple, one argument,
    void returning function with where you can give the url of an image and have
    it precahed like this?

    Any answer must work in IE5+.

    Thanks!


    Tags: None
    • Lasse Reichstein Nielsen
      #2
      Re: image precaching

      "viza" <none@example.i nvalid> writes:
      [color=blue]
      > This does not seem to work:[/color]

      HOW does it not work? I.e., what did you expect to happen and what really
      happens? And where do you put the code on a page?
      [color=blue]
      > function cacheimage(sour ce){
      > myimg=new Image()
      > myimg.src=sourc e
      > }
      > cacheimage('clo sed1.jpg')[/color]

      Nothing obviously wrong with the code. I would put semicolons after the
      statements for readability.
      [color=blue]
      > Is this because the myimg object is destroyed as soon as the function
      > returns,[/color]

      No, mostly because it isn't destroyed. You are assigning the new image
      to a global variable. Still, even local variables are usually not garbage
      collected soon enough to prevent the image from being fetched
      [color=blue]
      > or for some other reason?[/color]

      If it really doesn't work at all, it must be another reason.
      [color=blue]
      > Does anyone have a simple, one argument,
      > void returning function with where you can give the url of an image and have
      > it precahed like this?[/color]

      Yours look perfectly fine to me. Until we can see how it fails, it is hard
      to say anything else.

      /L
      --
      Lasse Reichstein Nielsen - lrn@hotpop.com
      Art D'HTML: <URL:http://www.infimum.dk/HTML/randomArtSplit. html>
      'Faith without judgement merely degrades the spirit divine.'

        Comment

        • viza
          #3
          Re: image precaching

          and then Lasse Reichstein Nielsen said:
          [color=blue]
          > "viza" <none@example.i nvalid> writes:[color=green]
          >> This does not seem to work:[/color]
          >
          > HOW does it not work? I.e., what did you expect to happen and what really
          > happens? And where do you put the code on a page?[/color]

          Try it:
          http://homepage.ntlworld.com/l_vajzovic/testcase.html


          It seems to be working in Moz at home, but IE5.0 at work seems to be not
          doing it.

            Comment

            • Janwillem Borleffs
              #4
              Re: image precaching


              "viza" <none@example.i nvalid> wrote in message
              news:bgal3g$ov$ 1@titan.btinter net.com...[color=blue]
              > Hi!
              >
              > This does not seem to work:
              >
              > function cacheimage(sour ce){
              > myimg=new Image()
              > myimg.src=sourc e
              > }
              > cacheimage('clo sed1.jpg')
              >
              > Is this because the myimg object is destroyed as soon as the function
              > returns, or for some other reason? Does anyone have a simple, one[/color]
              argument,[color=blue]
              > void returning function with where you can give the url of an image and[/color]
              have[color=blue]
              > it precahed like this?
              >
              > Any answer must work in IE5+.
              >
              > Thanks!
              >
              >[/color]

              Try this:

              function cacheimage(sour ce){
              window['myimg']=new Image()
              window['myimg'].src=source
              }

              This way, myimg will be a property of the window object, thus global.

              Otherwise, although you do not the var declaration, myimg will be caught up
              in the function's namespace only.


              JW



                Comment

                • Janwillem Borleffs
                  #5
                  Re: image precaching


                  "viza" <none@example.i nvalid> wrote in message
                  news:ih9Wa.88$A m1.34@newsfep1-gui.server.ntli .net...[color=blue]
                  > and then Lasse Reichstein Nielsen said:
                  >[color=green]
                  > > "viza" <none@example.i nvalid> writes:[color=darkred]
                  > >> This does not seem to work:[/color]
                  > >
                  > > HOW does it not work? I.e., what did you expect to happen and what[/color][/color]
                  really[color=blue][color=green]
                  > > happens? And where do you put the code on a page?[/color]
                  >
                  > Try it:
                  > http://homepage.ntlworld.com/l_vajzovic/testcase.html
                  >
                  > It seems to be working in Moz at home, but IE5.0 at work seems to be not
                  > doing it.
                  >[/color]

                  Which is quite amazing, because the file is incomplete. I have edited it
                  somewhat and now it works for me:

                  <html>
                  <head>
                  <title>testcase </title>
                  <script type="text/javascript">

                  function cacheimage(sour ce){
                  myimg=new Image()
                  myimg.src=sourc e
                  }
                  cacheimage('2.j pg')

                  window.onload = function () {
                  document.getEle mentById('imgid ').onclick = function (){
                  this.src=myimg. src;
                  }
                  }

                  </script>
                  </head>
                  <body>
                  <p>Click on the image to change it - it should happen instantly.
                  <p style="backgrou nd:#dddddd"><im g alt="" src="1.jpg" id="imgid">
                  </body>
                  </html>


                  JW



                    Comment

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