How does Jquery monitor the click events of dynamically created elements?

During the process of using Jquery, we may dynamically create elements such as li/button, but we cannot listen to the created elements using the following methods:

var domains = [{"id":1,"name":"测试1"},{"id":2,"name":"测试2"},{"id":3,"name":"测试3"}];
$.each(domains,function(key,domain){
$("#link_child").append('<li id="'+domain.id+'">'+domain.name+'</li>');
});
$("#link_child li").click(function(){
var linkChild = $(this).attr("id");
$("#link_child li").removeClass("active");
$(this).addClass("active");
});

We can use a new method to monitor clicks:

$(document).on('click','#link_child li',function(){
var id = $(this).attr("id");
$("#link_child li").removeClass("active");
$(this).addClass("active");
});