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Thread: CSS Background Image using a variable

  1. #1
    Join Date
    Jul 2010
    Posts
    3

    CSS Background Image using a variable

    Hi All,

    I am attempting to put a simple slideshow of pictures on our company's website as the background of a div. The code I have works fine for a single picture:

    obj.style.backgroundImage = 'url("photo.jpg")';

    but does not work when I try to use a variable for the file name instead of the file name itself, ie:

    obj.style.backgroundImage = 'url("processed[i].src")';

    Is there anyway to set the background image using variable names? I really don't want to have to use a switch statement with each case being a different picture. Any ideas?

    Thanks!

    Brian Rost

  2. #2
    Join Date
    Mar 2010
    Posts
    2,803
    In its simplest form maybe do the following:

    1) preload the slideshow images using javascript in the <head>

    2) create a window.onload function that uses setInterval() to then cycle through the images at whatever time period you want.

    Back 3-4 months ago I posted some example code in reply to a similar query.

  3. #3
    Join Date
    Jul 2010
    Posts
    3
    I have this code, and am just wondering about that one line that doesn't work the way I want it to. I'm not exactly sure what you're suggesting, could you elaborate? My javascript knowledge is limited, thanks

    <script language="JavaScript1.2">
    var HomeSlideArray=new Array()
    HomeSlideArray[0]="Images/photo1.jpg"
    HomeSlideArray[1]="Images/photo2.jpg"
    HomeSlideArray[2]="Images/photo3.jpg"
    HomeSlideArray[3]="Images/photo4.jpg"
    HomeSlideArray[4]="Images/photo5.jpg"
    HomeSlideArray[5]="Images/photo6.jpg"
    HomeSlideArray[6]="Images/photo7.jpg"
    HomeSlideArray[7]="Images/photo8.jpg"
    var speed=1
    var processed=new Array()
    for (i=0;i<HomeSlideArray.length;i++){
    processed[i]=new Image()
    processed[i].src=HomeSlideArray[i]
    }
    var inc=-1
    function slideback(){
    if (inc<HomeSlideArray.length-1)
    inc++
    else
    inc=0
    var obj = document.getElementById('main_image');
    obj.style.backgroundImage = 'url("processed[inc].src")';
    }
    if (document.all||document.getElementById)
    window.onload=new Function('setInterval("slideback()",speed)')
    </script>

  4. #4
    Join Date
    Mar 2010
    Posts
    2,803
    try

    Code:
     
    obj.style.backgroundImage = 'url("'+processed[inc].src+'")';
    so that processed[inc].src is actually evaluated and not taken as part of the string.
    Last edited by tirna; 07-08-2010 at 08:39 PM.

  5. #5
    Join Date
    Aug 2007
    Posts
    3,767
    Code:
    'url("'+processed[inc].src+'")'
    Some general suggestions.
    Code:
    <script type="text/javscript">
    var HomeSlideArray=["photo1.jpg","photo2.jpg","photo3.jpg","photo4.jpg","photo5.jpg","photo6.jpg","photo7.jpg","photo8.jpg"];
    var speed=1; // Every millisecond? Sure you don't mean 1000?
    var processed=[];
    for (i=0;i<HomeSlideArray.length;i++){
    processed[i]=new Image();
    processed[i].src="Images/"+HomeSlideArray[i];
    }
    var inc=-1
    function slideback(){
    if (inc<HomeSlideArray.length-1) {
        inc++;
    }
    else {
    inc=0;
    }
    document.getElementById('main_image').style.backgroundImage = 'url("'+processed[inc].src+'")';
    }
    window.onload=function() {setInterval(slideback,speed);};
    </script>
    If the picture names are that regular, it's even easier.
    Code:
    <script type="text/javscript">
    var no = 8
    var speed=1; // Every millisecond? Sure you don't mean 1000?
    var processed=[];
    for (i=0;i<no;i++){
    processed[i]=new Image();
    processed[i].src="Images/photo"+i+".jpg";
    }
    var inc=-1
    function slideback(){
    if (inc<no-1) {
        inc++;
    }
    else {
    inc=0;
    }
    document.getElementById('main_image').style.backgroundImage = 'url("'+processed[inc].src+'")';
    }
    window.onload=function() {setInterval(slideback,speed);};
    </script>
    Last edited by Declan1991; 07-08-2010 at 08:26 PM.

  6. #6
    Join Date
    Jul 2010
    Posts
    3
    Thanks! That worked perfectly. Thanks for the general code suggestions too, as I said my javascript knowledge isn't the best so the help is much appreciated

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