JavaScript控制图片加载完成后调用回调函数

这段代码可以控制指定区域内的图片加载完成后执行指定的回调函数。

function when_images_loaded($img_container, callback) { // do callback when images in $img_container (jQuery object) are loaded. Only works when ALL images in $img_container are newly inserted images and this function is called immediately after images are inserted into the target.
    var _imgs = $img_container.find('img'),
        img_length = _imgs.length,
        img_load_cntr = 0;
 
    if (img_length) { //if the $img_container contains new images.
        _imgs.on('load', function() { //then we avoid the callback until images are loaded
            img_load_cntr++;
            if (img_load_cntr == img_length) {
                callback();
            }
        });
    }
    else { //otherwise just do the main callback action if there's no images in $img_container.
        callback();
    }
}