// $Id: rollover_images.js 4458 2006-10-03 09:00:59Z henry $
// Henry Todd, Hildebrand
/*============================================================================
Image swapping script (rollover images) with preloading.
Example Usage:
So long as this script is loaded on the page, and there is an "_over" version
of example.jpg in the images dir (/images/example_over.jpg) it will be
preloaded ready for the mouse events. The key things are the naming of the
"_over" version of the image, and the assignment of the "rollover" class to
the ![]()
.
GOTCHA: the image filenames can only contain one dot (".")
============================================================================*/
function preloadImages() {
/*
* This function is to be called by the onload event handler
* It will attempt to preload rollover images for any ![]()
s
* that it finds with the "rollover" class assigned to them.
*/
var images = document.getElementsByTagName("img");
var rollovers = new Array();
for (var i = 0; i < images.length; i++) {
var img = images[i];
if (img.className == "preload") {
// we're looking at an ![]()
with an associated rollover
// build the URL for the rollover graphic to preload
var rollover = new Image();
rollover.src = calculateImagePath(img.src);
rollovers.push(rollover);
}
}
return true;
}
function swap(image) {
image.src = calculateImagePath(image.src);
return true;
}
function calculateImagePath(path) {
// TODO?: use regex to find last dot instead of assuming there's only one
bits = path.split("_over");
if (bits.length == 1) {
// no match, the path doesn't contain "_over", so add it
var path_components = bits[0].split(".");
var rollover_path = "";
var filename = path_components.length - 2;
path_components[filename] += "_over";
return path_components.join(".");
} else if (bits.length == 2) {
// a match, the path contains "_over", so remove it
return bits[0] + bits[1];
} else {
// error, string contains more than one "_over" substring
}
}
function pageSwap(title, image) {
var sectiontitle = document.getElementById('sectiontitle');
if (sectiontitle) {
// only attempt to alter the title if it exists
sectiontitle.textContent = title; // w3c
sectiontitle.innerText = title; // IE
}
var sectionimage = document.getElementById('sectionimage');
if (sectionimage) {
// only attempt to alter the image if it exists
sectionimage.src = image;
}
}