Question

我正在使用ArrayList作为我的数组，

let ArrayList   =  ['a','b','c','d','e','f'];

我在方法1和方法2之间感到困惑，因为在两种情况下，我都引用了ArrayList，您还可以通过此链接https://jsfiddle.net/mnjsnj/u1fms8wx/2/检查日志

方法1

let Method1 = ArrayList;  // Referenced arrayList by another variable 
ArrayList= []; // Empty the array 
console.log(Method1); // Output ['a','b','c','d','e','f']

方法2

let Method2 = ArrayList;  // Referenced arrayList by another variable 
ArrayList.length = 0; // Empty the array by setting length to 0
console.log(Method2 ); // Output []

Answer 1

ArrayList在第一种方法后将被清空，因此您正在为Method2

分配一个空数组

let ArrayList = ['a', 'b', 'c', 'd', 'e', 'f'];

let Method1 = ArrayList; // Referenced arrayList by another variable 
ArrayList = []; // Empty the array 
console.log(Method1); // Output ['a','b','c','d','e','f']

console.log('ArrayList after Method1....!' , ArrayList)
// here an empty array is assinged to Method2
let Method2 = ArrayList; // Referenced arrayList by another variable 
ArrayList.length = 0; // Empty the array by setting length to 0
console.log(Method2); // Output []

Answer 2

了解这里发生的事情的技巧是了解变量在JavaScript中的工作方式以及赋值（=）运算符的作用。

变量只是绑定到存储位置的名称。

当我们通过=运算符将某物分配给变量时，我们仅更改该变量指向的内容，而不更改现有内存位置的实际数据，而只是使该变量不指向它了。

// Method1 now points to the same memory location as ArrayList
let Method1 = ArrayList;
// ArrayList variable now points to a new memory location containing an empty array
ArrayList = []; 
// Method1 is still pointing to the original memory location so the array is unaffected
console.log(Method1);

在第二个示例中，您将ArrayList更改为length，直接影响了0指向的存储位置上的数据。

// point Method2 variable to the same location as ArrayList variable
let Method2 = ArrayList; 
// change the data stored at the location ArrayList is pointing to
ArrayList.length = 0; // Empty the array by setting length to 0
// Since Method2 is also pointing to that location, we see the empty array
console.log(Method2); // Output []

如何在JavaScript中清空数组？

2 个答案: