什么更快？运行一个空函数或检查函数是否未定义？ [英] What is faster? Running an empty function or checking if function is undefined?

问题描述

我正在编写一些代码，其中一个作为参数传入的函数有时可能是未定义的。对这种糟糕的实践感到好奇，我想知道实际上速度更快？给一个空函数，或者让函数检查参数是否未定义？

我做了以下测试来尝试。答案非常令人惊讶！

  var timesTest = 1000; 
 
函数empty（）{} 
 console.time（'运行一个空函数'）; 
 for（var i = 0; i< timesTest; i ++）{
 empty（）; 
} 
 console.timeEnd（'运行一个空函数'）; 
 
 var somethingthatdoesnotexist; 
 console.time（'检查函数是否存在'）; 
 for（var i = 0; i< timesTest; i ++）{
 if（somethingthatnoteesxist）{
 somethingthatdoesnotexist（）; 
} 
} 
 console.timeEnd（'检查函数是否存在'）; 
 
 //结果：
 //运行一个空函数：0.103ms 
 //检查函数是否存在：0.036ms 
  

在数字较小的情况下，检查未定义参数的速度要快得多。

一旦测试时间增加，事情就会变得有趣。

  // var timesTest = 100000; 
 //结果：
 //运行一个空函数：1.125ms 
 //检查函数是否存在：1.276ms 
  

和

  //结果：
 // var timesTest = 1000000000; 
 //运行一个空函数：2096.941ms 
 //检查函数是否存在：2452.922ms 
  

随着测试数量的增长，运行空白函数的速度变得更快一些。

我还没有试图在图上绘制这个图，但我对这种行为很好奇。有人知道为什么吗？如何影响现实世界中的代码？ http://jsperf.com ，以获得更准确的基准和花哨图表。我做了一个： http://jsperf.com/empty-vs-check

这是微型优化。 NOBODY会注意到差异。 10亿次迭代的差异不到半秒，这绝不会发生。做你认为更可读的东西;不要担心表演。

I was writing some code where a function being passed in as an argument might sometimes be undefined. Being curious about this as bad 'practice', I wondered what is actually faster? Giving an empty function, or having the function check if the argument was undefined?

I did the following test to try. The answer was very surprising!

var timesTest = 1000;

function empty(){}
console.time('running an empty function');
for( var i=0; i<timesTest; i++ ){
  empty();
}
console.timeEnd('running an empty function');

var somethingthatdoesnotexist;
console.time('checking if a function exists');
for( var i=0; i<timesTest; i++ ){
  if( somethingthatdoesnotexist ){
    somethingthatdoesnotexist();
  }
}
console.timeEnd('checking if a function exists');

// results:
// running an empty function: 0.103ms
// checking if a function exists: 0.036ms

At low numbers, checking for undefined argument is much faster.

Things get interesting once the times tested increases.

// var timesTest = 100000;
// results:
// running an empty function: 1.125ms
// checking if a function exists: 1.276ms 

and

// results:
// var timesTest = 1000000000;
// running an empty function: 2096.941ms
// checking if a function exists: 2452.922ms 

As the number of tests grew, running a blank function becomes a bit faster by a margin.

I haven't tried plotting this out on a graph yet, but I'm curious as to this behavior. Does anyone know why this is? How does this affect things in real world code?

解决方案

1. http://jsperf.com for more accurate benchmarking and fancy graphs. I made one: http://jsperf.com/empty-vs-check

2. This is micro-optimization. NOBODY WILL EVER NOTICE A DIFFERENCE. There's a difference of less than a half a second for a billion iterations, which will never happen. Do what you think is more readable; don't worry about performance.

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