SOURCE

var test = '<img class="lazy" data-src="https://www.baidu.com/img/bd_logo1.png">';

$(document).ready(function(){
  setTimeout(function(){
    $(".app").append(test)
    $(".lazy").lazyload({
  		effect : "slideDown",
		});
  },10000)
});
console.log(1)

<div id="app" class="app">
   
</div>

.app{
  background-color:#ffffff
}