Example code for delayed loading of JS images based on mouse scrolling_javascript skills

Recently, I studied the implementation of JD.com using jQuery as follows:
is the default address assigned to the src2 attribute of the img tag, and the src attribute value is assigned to it when displayed.

Copy code The code is as follows:

function lazyload(option) {
var settings = {
defObj: null,
defHeight: 0
};
settings = $.extend(settings, option || {});
var defHeight = settings.defHeight;
var defObj = (typeof settings.defObj == "object") ? settings.defObj.find("img") : $(settings.defObj).find("img");
var pageTop = function() {
return document.documentElement.clientHeight Math.max(document.documentElement.scrollTop, document.body.scrollTop) - settings.defHeight;
};
var imgLoad = function() {
defObj. each(function() {
if ($(this).offset().top <= pageTop()) {
var src2 = $(this).attr("src2");
//What has been displayed does not need to be displayed again
if (src2) {
                                                                                                     ;
}
           }
});
     };
        imgLoad(); );
});
}
lazyload({
defObj:".w1"
});