Image prefetch with javascript

In order to perform image prefetching with javascript we need to create an Image object and insert an url in its 'src' global variable, as follows:

var img = new Image()
img.src = 'http://my_url.jpg'

Then we can attach handlers in order to be advised when fetching operation completes or when it goes wrong:

img.onload = function() {
// remove placeholder and show image
}

img.onerror = function() {
// remove placeholder and print that image loading went wrong
}

That's all, enjoy