A piece of js code that implements delayed loading of images on the page_image special effects

lazyLoad=(function() {
var map_element = {};
var element_obj = [];
var download_count = 0;
var last_offset = -1;
var doc_body;
var doc_element;
var lazy_load_tag; body;
doc_element = document.compatMode == 'BackCompat' ? doc_body: document.documentElement;
lazy_load_tag ​​= tags || ["img", "iframe"];
};
function initElementMap () {
var all_element = [];
//Find out the elements that need to be delayed loaded from all related elements
for (var i = 0,
len = lazy_load_tag.length; i < len; i ) {
var el = document.getElementsByTagName(lazy_load_tag[i]);
for (var j = 0,
len2 = el.length; j < len2; j ) {
if (typeof(el[j]) == "object" && el[j].getAttribute("lazy_src")) {
element_obj.push(all_element[key]);
}
}
}

for (var i = 0,
len = element_obj.length; i < len; i ) {
var o_img = element_obj[i];
var t_index = getAbsoluteTop(o_img);//Get the top distance of the image relative to the document
if (map_element[t_index]) {
map_element[t_index].push(i);
} else {
//Save a queue according to the distance above
var t_array = [];
t_array[0] = i;
map_element[t_index] = t_array;
download_count;//Requires delayed loading Number of pictures
}
}

};
function initDownloadListen() {
if (!download_count) return;
var offset = (window.MessageEvent && !document .getBoxObjectFor) ? doc_body.scrollTop: doc_element.scrollTop;
//The offset of the visual area = the height of the document
var visio_offset = offset doc_element.clientHeight;
if (last_offset == visio_offset) {
setTimeout(initDownloadListen, 200);
return;
}
last_offset = visio_offset;
var visio_height = doc_element.clientHeight;
var img_show_height = visio_height offset;
for (var key in map_element) {
if (img_show_height > key) {
var t_o = map_element[key];
var img_vl = t_o.length;
for (var l = 0; l < img_vl; l ) {
element_obj[t_o[l]].src = element_obj[t_o[l]].getAttribute("lazy_src");
}
delete map_element[key];
download_count-- ;
}
}
setTimeout(initDownloadListen, 200);
};
function getAbsoluteTop(element) {
if (arguments.length != 1 || element == null ) {
return null;
}
var offsetTop = element.offsetTop;
while (element = element.offsetParent) {
offsetTop = element.offsetTop;
}
return offsetTop;
}
function init(tags) {
initVar(tags);
initElementMap();
initDownloadListen();
};
return {
init: init
}
})();


Usage: Change the src of the image that needs to be delayed loaded on the page to lazy_src, and then put the above js into the body At the end, call: lazyLoad.init();

chlid.find("img[init_src]").each(function(){
$(this).attr("src",$(this).attr("init_src"));
$ (this).removeAttr("init_src");
});