simple img preload

loadImg.js

var loadImg = function(src, handle_once, handle_done) {
    var _len = src.length ;
    var _load = function( i ) {
        if (i >= _len) {
            handle_done();
            return  ;   
        }
        
        var img = new Image();
        img.src = src[i];
        img.addEventListener('load', function () {
            i++;
            handle_once(Math.ceil(100 * i / _len));
            _load(i);
            img = null;
        }, false);
    }
 
    _load(0);
};

var loadImgCustom = function (imgs, prefix, cb, cbAll, debug) {
    prefix = !!debug ? 'images/' : prefix;
    for (var i = 0, k = null; k = imgs[i] ; i++ ) {
        imgs[i] = prefix + k;
    }
    loadImg(imgs, function (n) {
        cb(n);
    }, function () {
        cbAll();
    });
};