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Random Image Display Using JavaScriptThe steps involved in randomly displaying an image from a set are very similar to those used for displaying random text strings.
var img_name = new Array("purple.gif", "red.gif",
"blue.gif", "yellow.gif", "green.gif", "pink.gif");
var l = img_name.length;
var rnd_no = Math.floor(l*Math.random());
document.r_img.src = img_name[rnd_no];
<img src="purple.gif" width="100" height="50"
name="r_img" alt="Random image" />
In th code above, we have JavaScript array containing 6 images. The array length found from length is, thus, 6 - img_name[0] would be "purple.gif", img_name[1] would be "red.gif" and so on. We then use the Math.round() to get a random number, multiply it with the array length and round it up using Math.floor().
Click to display another random image. Note: Array are zero-indexed, so the last element in the array will the length of the array minus 1. However, since we are employing floor() to get an integer, we can use the value from ARRAY_NAME.length directly. You can also use the id attribute of the image tag instead of name; as:
var img_name = new Array("purple.gif", "red.gif",
"blue.gif", "yellow.gif", "green.gif", "pink.gif");
var l = img_name.length;
var rnd_no = Math.floor(l*Math.random());
document.getElementById("randomimage").src = img_name[rnd_no];
<img src="purple.gif" width="100" height="50"
id="randomimage" alt="Random image" />
Click to display another random image. When can you display random images on a web page?A potential use of the random image displaying code is when you want to show a single banner from a set - though I would prefer using server-side scripts like PHP or Perl for this. I have also employed the code to randomly rotate images at a designated place on the web page. 
Page contents: Displaying random images on web page using javascript - random image display on web page
Page URL: http://www.webdevelopersnotes.com/tutorials/javascript/ random_image_display_javascript.php3
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