image preloader

preloader.js

function preload(list, callback, imageCallback) {
    var at = len = list.length;
    return list = list.map(function (item) {
        var pItem = new Image();
        pItem.onload = function (i) {
            imageCallback && imageCallback.call(this, this, len-at, len);
            if (!--at) {
                callback(list);
            }
        };
        pItem.src = item;
        return pItem;
    });
}

preloader.min.js

function preload(l,c,i){var a=b=l.length;return l=l.map(function(t){var p=new Image;p.onload=function(){i&&i.call(this,this,b-a,b);!--a&&c(l)};p.src=t;return p})};