查看控制台，每次时间都不一样，我不知道为什么
我正在尝试执行一个函数并获取它所花费的时间，我使用了console.time()，但是每次运行时它都显示不同的时间 另一件事是，下划线所花费的时间是否超过正常执行时间。
function map(){
console.time('mycode');
var arr = [234345345,345346,5445645,456456,456456,234,467,234234234,456,43535,456,12,3123123123,456,456456,1231235,6456456,234,234456,4,5632452344,65,543452334124436,2345,345346,5445645,456456,456456,234,467,234234234,456,43535,456,12,3123123123,456,456456,1231235,6456456,234,234456,4,5632452344,65,543452334124436,2345,345346,5445645,456456,456456,234,467,234234234,456,43535,456,12,3123123123,456,456456,1231235,6456456,234,234456,4,5632452344,65,543452334124436,2345,345346,5445645,456456,456456,234,467,234234234,456,43535,456,12,3123123123,456,456456,1231235,6456456,234,234456,4,5632452344,65,543452334124436,2345,345346,5445645,456456,456456,234,467,234234234,456,43535,456,12,3123123123,456,456456,1231235,6456456,234,234456,4,5632452344,65,543452334124436,2345,345346,5445645,456456,456456,234,467,234234234,456,43535,456,12,3123123123,456,456456,1231235,6456456,234,234456,4,5632452344,65,543452334124436,2345,345346,5445645,456456,456456,234,467,234234234,456,43535,456,12,3123123123,456,456456,1231235,6456456,234,234456,4,5632452344,65,543452334124436,2345,345346,5445645,456456,456456,234,467,234234234,456,43535,456,12,3123123123,456,456456,1231235,6456456,234,234456,4,5632452344,65,543452334124436,2345,345346,5445645,456456,456456,234,467,234234234,456,43535,456,12,3123123123,456,456456,1231235,6456456,234,234456,4,5632452344,65,543452334124436,2345,345346,5445645,456456,456456,234,467,234234234,456,43535,456,12,3123123123,456,456456,1231235,6456456,234,234456,4,5632452344,65,543452334124436,2345,345346,5445645,456456,456456,234,467,234234234,456,43535,456,12,3123123123,456,456456,1231235,6456456,234,234456,4,5632452344,65,543452334124436,2345,345346,5445645,456456,456456,234,467,234234234,456,43535,456,12,3123123123,456,456456,1231235,6456456,234,234456,4,5632452344,65,543452334124436,2345,345346,5445645,456456,456456,234,467,234234234,456,43535,456,12,3123123123,456,456456,1231235,6456456,234,234456,4,5632452344,65,543452334124436,2345,345346,5445645,456456,456456,234,467,234234234,456,43535,456,12,3123123123,456,456456,1231235,6456456,234,234456,4,5632452344,65,543452334124436,2345,345346,2345];
var result = [];
var constant = 3;
var length = arr.length; //will avoid calculation of length each time
for(i=0;i<length;i++){
temp = arr[i] * constant;
result.push(temp);
}
console.timeEnd('mycode');
console.time('mycode1');
var underscore = _.map([arr], function(num){ return num * 3; });
console.timeEnd('mycode1');
}
function where(){
console.time("myCode");
var arr = [{title: "Cymbeline", author: "Shakespeare", year: 1611},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615},
{title: "The Tempest", author: "Shakespeare", year: 1613},
{title: "The Tempest", author: "Shakespeare", year: 1615}
];
var author = 'Shakespeare';
var year = '1611';
var result = [];
var length = arr.length; //will avoid calculation of length each time
for(i=0;i<length;i++){ //you know that and takes more time than or statement
if(arr[i]['author'] == author && arr[i]['year'] == year){
result.push(arr[i]);
}
}
console.log(result)
console.timeEnd("myCode");
console.time("myCode1");
var underscore = _.filter(arr, {author: "Shakespeare", year: 1611});
console.log(underscore)
console.timeEnd("myCode1");
}.container{
width:calc(100% - 200px);
text-align:center;
margin:0 auto;
background:#f4f4f4;
}<script src="http://underscorejs.org/underscore-min.js"></script>
<h1>Evaluating time </h1>
<input type='button' onclick='map()' value='Execute'>
<input type='button' onclick='where()' value='Execute'>
最佳答案
执行代码所需的时间会因 CPU 正在执行的其他工作而异。由于计算机上正在运行其他进程，中断不断发生。您的 Web 应用程序只是需要一定 CPU 时间的众多应用程序之一。还有一些因素，例如 CPU 对频繁请求的数据执行的缓存以及操作系统缓存。
关于javascript - 为什么执行相同的 JavaScript 代码所花费的时间不同，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/37986905/