jQuery中$(function())的作用

$(function(){//五分钟无操作，返回系统首页,timeToreturn.js
 function timeToReturn(){
 window.location.href = "http://localhost:8080/zhongCourt/";
 }
 var nowtime = Date.parse(new Date());
 var timeend = Date.parse(new Date());
 
 $("body").click(function(){
 nowtime = Date.parse(new Date());
 console.log("nowtime" + nowtime); 
 });
 
 function check(){
 timeend = Date.parse(new Date());
 console.log("check");
 if((timeend - nowtime) > 300000){
 timeToReturn();
 }
 setTimeout(check,10000);
 }
 setTimeout(check,10000);
 
})