I am a javascript newbie... I'm trying to write a function that grabs a random image from a directory and sets it as the background image of my banner div. I also need to set the size of the image and for it not to repeat. Here's what I've got so far, and it's not quite working. What am I missing?

$(function() {

// some other scripts here

  function bg() {

    var imgCount = 3;
    // image directory
    var dir = '/';
    // random the images
    var randomCount = Math.round(Math.random() * (imgCount - 1)) + 1;
    // array of images & file name
    var images = new Array();
    images[1] = '001.png',
    images[2] = '002.png',
    images[3] = '003.png',

    document.getElementById('banner').style.backgroundImage = "url(' + dir + images[randomCount] + ')";
    document.getElementById('banner').style.backgroundRepeat = "no-repeat";
    document.getElementById('banner').style.backgroundSize = "388px";
  }

}); // end doc ready

I am a javascript newbie... I'm trying to write a function that grabs a random image from a directory and sets it as the background image of my banner div. I also need to set the size of the image and for it not to repeat. Here's what I've got so far, and it's not quite working. What am I missing?

$(function() {

// some other scripts here

  function bg() {

    var imgCount = 3;
    // image directory
    var dir = 'http://local.statamic./_themes/img/';
    // random the images
    var randomCount = Math.round(Math.random() * (imgCount - 1)) + 1;
    // array of images & file name
    var images = new Array();
    images[1] = '001.png',
    images[2] = '002.png',
    images[3] = '003.png',

    document.getElementById('banner').style.backgroundImage = "url(' + dir + images[randomCount] + ')";
    document.getElementById('banner').style.backgroundRepeat = "no-repeat";
    document.getElementById('banner').style.backgroundSize = "388px";
  }

}); // end doc ready

• javascript
• background-image

• Are you actually invoking your bg function anywhere? The code above just defines it, but doesn't run it. Also, replace the mas after images[x]='' with semicolons. – christian314159 Commented Jun 25, 2014 at 22:10
• You were partly correct - I forgot to call my function. But also, the mas on the URL were incorrect. They should have been: "url(" + dir + images[randomCount] + ")"; – FixMySync Commented Jun 26, 2014 at 0:41
• ... and by 'mas' I meant quotation marks. ;) – FixMySync Commented Jun 26, 2014 at 4:29

2 Answers 2

I messed around with this for a while, and I came up with this solution. Just make sure you have some content in the "banner" element so that it actually shows up, because just a background won't give size to the element.

function bg() {

   var imgCount = 3;
   var dir = 'http://local.statamic./_themes/img/';
   // I changed your random generator
   var randomCount = (Math.floor(Math.random() * imgCount));
   // I changed your array to the literal notation. The literal notation is preferred.
   var images = ['001.png', '002.png', '003.png'];
   // I changed this section to just define the style attribute the best way I know how.
   document.getElementById('banner').setAttribute("style", "background-image: url(" + dir + images[randomCount] + ");background-repeat: no-repeat;background-size: 388px 388px");
}
// Don't forget to run the function instead of just defining it.
bg();

Here's something sort of like what I use, and it works great. First, I rename all my background images "1.jpg" through whatever (ex. "29.jpg" ). Then:

var totalCount = 29;
function ChangeIt() 
{
var num = Math.ceil( Math.random() * totalCount );
document.getElementById("div1").style.backgroundImage = 'images/'+num+'.jpg';
document.getElementById("div1").style.backgroundSize="100%";
document.getElementById("div1").style.backgroundRepeat="fixed";
}

Then run the function ChangeIt() .