js中引用类型之日期

var date = new Date();
date.getFullYear(); //年
date.getMonth(); //月
date.getDate(); //日

var date1 = new Date(2017,0,1);
var date2 = new Date(2017,11,1);
alert(date1 < date2); //true

function spend(start){
var stop = Date.now();
console.log(stop - start);
}
var start = Date.now();
setTimeout(spend,5000); //5001

function spend(start){
var stop = +new Date(); //使用"+"操作符将Date对象转换为字符串
console.log(stop - start);
}
var start = +new Date();
setTimeout(spend,5000); //5001