简单的Javascript代码中的奇怪问题，非空数组参数到达函数为空(Strange issue in simple Javascript code, non-empty array parameter reaches function empty)

 我最近一直在练习JS / ECMAScript我在网上找到的例子，在尝试一个关于反转数组的例子时，我遇到了一个非常奇怪的问题。 我下面的代码是完整的，但是半工作。 
 
"use strict";

function reverseArray(theArray){
  let tempArray = [];

  if(theArray && theArray.length > 0){
    console.log('Here works!');
    while(theArray.length > 0){
      tempArray.unshift(theArray.shift());
    }
  }

  return tempArray;
}

function reverseArrayInPlace(theArray){
  console.log(theArray);
  if(theArray && theArray.length > 0){
    console.log('Should go through here!');
    for(let i = 0; i < Math.floor(theArray.length/2); i++){
      let temp = theArray[i];
      theArray[i] = theArray[theArray.length - 1 - i];
      theArray[theArray.length -1 - i] = temp;
    }
  }

  return theArray;
}

let firstSacrifice = ['I','n','v','e','r','t','M','E'];
let secondSacrifice = ['I','n','v','e','r','t','M','E','A','g','a','i','N'];

console.log(firstSacrifice);
console.log('InvertME >>', reverseArray(firstSacrifice));
console.log('InvertME >>', reverseArrayInPlace(firstSacrifice));
console.log('\n');
console.log(secondSacrifice);
console.log('InvertMEAgaiN >>', reverseArray(secondSacrifice));
console.log('InvertMEAgaiN >>', reverseArrayInPlace(secondSacrifice));
 
 第一个函数reverseArray按预期工作：它将给定的数组复制到另一个数组中。 问题在于第二个函数reverseArrayInPlace 。 从理论上讲，它应该在它收到的同一个给定数组中进行反转，但奇怪的是，参数theArray到达函数empty [] 。 因此，根本没有完成该功能的逆转。 
 
 我正在使用node （v6.10）在shell上测试代码，但在这种情况下，我也在firefox ， chrome和edge的控制台中执行它，结果非常相似。 由于某种原因，我无法理解（和往常一样，这种愚蠢的错误，我已经尝试了几个小时），参数theArray在到达时是空的，当然，根本没有给出任何错误或警告。 
 
 顺便说一下，我在本教程中找到了关于Javascript的练习。 我知道它有点老了（是的，我已经阅读过关于MDN上JS的文档）但是为了实践起见，提出的练习很有趣。 
 
 哦， 如果你想摆弄这段代码 ， 请点击这里 ，但记得打开控制台查看日志条目！ 
 
 谢谢！ 

I've been practising JS/ECMAScript lately with examples that I find on the net and while trying one about reversing arrays, I've hit a really strange problem. The code that I put below is complete but half-working. 
 
"use strict";

function reverseArray(theArray){
  let tempArray = [];

  if(theArray && theArray.length > 0){
    console.log('Here works!');
    while(theArray.length > 0){
      tempArray.unshift(theArray.shift());
    }
  }

  return tempArray;
}

function reverseArrayInPlace(theArray){
  console.log(theArray);
  if(theArray && theArray.length > 0){
    console.log('Should go through here!');
    for(let i = 0; i < Math.floor(theArray.length/2); i++){
      let temp = theArray[i];
      theArray[i] = theArray[theArray.length - 1 - i];
      theArray[theArray.length -1 - i] = temp;
    }
  }

  return theArray;
}

let firstSacrifice = ['I','n','v','e','r','t','M','E'];
let secondSacrifice = ['I','n','v','e','r','t','M','E','A','g','a','i','N'];

console.log(firstSacrifice);
console.log('InvertME >>', reverseArray(firstSacrifice));
console.log('InvertME >>', reverseArrayInPlace(firstSacrifice));
console.log('\n');
console.log(secondSacrifice);
console.log('InvertMEAgaiN >>', reverseArray(secondSacrifice));
console.log('InvertMEAgaiN >>', reverseArrayInPlace(secondSacrifice));
 
The first function, reverseArray, works as expected: it copies the given array into another. The problem comes with the second function, reverseArrayInPlace. In theory, it should do the reversal in the same given array it receives but, strangely, the parameter theArray reaches that function empty []. Therefore, no reversal done with that function at all. 
 
I'm testing the code on a shell with node (v6.10), but in this case I also executed it in the consoles of firefox, chrome and edge with the very same result. For some reason that I cannot fathom (and as usual with this kind of silly errors, I've been trying for a good few hours), the parameter theArray is empty on arrival and, of course, no errors or warnings are given at all.
 
By the way, I found the exercise proposed in this tutorial about Javascript. I know it's a bit old (and yes, I've already read the docs about JS on MDN) but the exercises proposed there are interesting enough for practice's sake.
 
Oh, and click here if you want to fiddle with this code, but remember to open the console to see the log entries!
 
Thanks!

原文：https://stackoverflow.com/questions/42847142