图片预加载之模拟img.load()

function imgBatchLoad()
{
var instance = this;
this.loadCount = 0;
this.images = [];
this.imgCount = 0;
this.progress = 0;
this.load = function(pathArray)
    {
        instance.imgCount = pathArray.length;
for(var i=0;i<pathArray.length;i++)
        {
var imgDom = new Image();
            imgDom.src = pathArray[i];
            imgDom.onload = updateProgress(imgDom,i);
        }
    };
this.onload = function()
    {

    };
this.onProgress = function()
    {

    };
function updateProgress(img,index)
    {
return function(){
            instance.loadCount++;
            instance.images[index] = img;
            instance.progress = instance.loadCount / instance.imgCount*100;
            instance.onProgress(instance.progress);
if(instance.loadCount == instance.imgCount)
            {
                instance.onload(instance.images);
            }

        }
    }
}