如何在 JavaScript 中清空数组？ [复制]

Question

我使用 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，因为在这两种情况下，我都引用了另一个 ArrayList，您还可以通过此链接查看日志https://jsfiddle.net/mnjsnj/u1fms8wx/2/

方法一

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

方法二

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

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

变量只是内存位置的绑定名称。

当我们通过= 操作符给变量赋值时，我们只改变变量指向的东西，我们没有改变现有内存位置的实际数据，我们只是让变量不指向它不再。

// 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，您通过将length 更改为0 来直接影响ArrayList 指向的内存位置上的数据。

// 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 []

Answer 2

ArrayList 在第一种方法之后被清空，因此您将一个空数组分配给Method2

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 []