为什么来自Eloquent JavaScript的这个函数示例返回值24？ [英] Why does this function example from Eloquent JavaScript return the value 24?

问题描述

我是JavaScript新手，想要从书中理解一个例子。当我通过这个例子时，我预计fac（4）的值是12.这将是（4 - 1）* 4的结果。然而，

然而， ，当我在 http://eloquentjavascript.net/00_intro上运行在线书籍（页面底部附近）的代码时。 html ，我得到的值是24.我在这里错过了什么？

  function fac（n）{
 if（n == 0）
 return 1; 
 else 
 return fac（n  -  1）* n; 
} 
 console.log（fac（4））; 
  

我试图通过Twitter和在线调查找到答案，但都不成功。我知道我忽略了一些东西，但似乎无法看到它。 解决方案

因为它是递归的。

 函数fac（n）{
 if（n == 0）
 return 1; 
 else 
 return fac（n  -  1）* n; 
} 
 console.log（fac（4））; 
  

所以让我们来追踪它
$ b $ pre > fac（3）* 4;
fac（2）* 3 * 4;
fac（1）* 2 * 3 * 4;
fac（0）* 1 * 2 * 3 * 4;
1 * 1 * 2 * 3 * 4;


当然，这是24。

I am new to JavaScript and am trying to understand an example from the book. When I step through this example, I expect the value of fac(4) to be 12. That would be the result of (4 - 1) * 4.

However, when I run the code from the online book (near bottom of page) at http://eloquentjavascript.net/00_intro.html, I get the value 24. What am I missing here?

function fac(n) {
  if (n == 0)
    return 1;
  else
    return fac(n - 1) * n;
}
console.log(fac(4));

I have tried to find an answer through Twitter and through online research but have been unsuccessful. I know I am overlooking something, but can't seem to see it.

解决方案

Because it is recursive.

function fac(n) {
  if (n == 0)
    return 1;
  else
    return fac(n - 1) * n;
}
console.log(fac(4));

So let's trace it

fac(3) * 4;
fac(2) * 3 * 4;
fac(1) * 2 * 3 * 4;
fac(0) * 1 * 2 * 3 * 4;
1 * 1 * 2 * 3 * 4;

And of course, that is 24.

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