return !function() 与 return function() ? false : t

Question

学习 《JavaScript DOM编程艺术 第2版》（中文）时候遇到的问题links[i].onclick = function() {    return !showPic(this); // showPic(this) ? false : true}我自己试了试，两者结果一样，这两种方法在执行效率上有什么区别吗？

Answer 1

这两种方式都是使用最基本的操作符，效率应该是一样的。

写了一段脚本实测了一下：

var t1 = Date.parse(new Date());                                                    
var a = true;                                                                       
function set_a(p) {                                                                 
  var tmp = !p;                                                                     
  return tmp;                                                                       
}                                                                                   
for (var i=0; i<1000000000; i++) {                                                  
  a = a ? false : true;                                                             
}                                                                                   
var t2 = Date.parse(new Date());                                                    
console.log(t2-t1);                                                                 
                                                                                    
                                                                                    
for (var i=0; i<1000000000; i++) {                                                  
  a = !a;                                                                           
}                                                                                                                                                                                           
var t3 = Date.parse(new Date());                                                    
console.log(t3-t2);

Result:

[root@iZ94dn8i2nsZ js]# node answer.js 20002000

两种方式分别运行了十亿此，使用了2000ms，也就是分别跑了2秒钟时间。

效率一样。