这段js代码是什么意思呀？

Question

var start = Date.now();var response = prompt("What is your name?", "");var end = Date.now();var elapsed = (end - start) / 1000;document.write("You took " + elapsed + " seconds" + " to type: " + response);为什么start和end都是Date.now()? 还有elapsed=(end-start)/1000是什么意思啊？

Answer 1

Date.now()
都是取当前时间啊
end和start执行的时间不同可以取出时间差得出花费了多少时间

var start = Date.now();

setTimeout(function(){

    var end = Date.now();

    console.log(end-start);

},2000);