prelaod っぽいやつ

preload

(function (global, document) {
    var imgList = [
        "http://cdn1.iconfinder.com/data/icons/CrystalClear/128x128/mimetypes/pdf.png",
        "http://cdn1.iconfinder.com/data/icons/CrystalClear/128x128/mimetypes/unknown.png",
        "http://cdn1.iconfinder.com/data/icons/CrystalClear/128x128/mimetypes/document.png",
        "http://cdn4.iconfinder.com/data/icons/CV_icons_by_miffo/128/references.png",
        "http://cdn2.iconfinder.com/data/icons/oxygen/128x128/mimetypes/application-vnd.oasis.opendocument.text.png"
    ];

    preload(imgList, "imgOnLoaded");

    document.addEventListener("imgOnLoaded", function () {
        console.log("全部読み終わったよー");
    }, false);

    function preload(data, callbackName) {
        if (!data.length) return;

        var event = document.createEvent("Event"),
            callback = function () {
                event.initEvent(callbackName, false, false);
                document.dispatchEvent(event);
                return this;
            },
            img = [],
            count = 0;

        for (var i = 0, len = data.length; i < len; i++) {
            img[i] = new Image();
            img[i].src = data[i];

            img[i].addEventListener("load", loadHandler(img[i]), false);
            img[i].addEventListener("error", loadHandler(undefined), false);
        }

        function loadHandler(data) {
            return function () {
                count++;
                console.log("loaded: " + data.src);

                if (data !== undefined) gc(data);
                if (count === img.length) callback(callbackName);
            };
        }

        function gc(data) {
            data.removeEventListener("load", loadHandler, false);
        }
    }
})(this, document);