将JavaScript中的数组复制到另一个数组时:

var arr1 = ['a','b','c'];
var arr2 = arr1;
arr2.push('d');  //Now, arr1 = ['a','b','c','d']

我意识到arr2指的是与arr1相同的数组,而不是一个新的独立数组。如何复制阵列以获得两个独立的阵列?


当前回答

在研究之后,我发现一个干净的方法可以是:

  const arr1 = [['item 1-1', 'item 1-2'], ['item 2-1', 'item 2-2'], ['item 3-1', 'item 3-2']];

  /**
   * Using Spread operator, it will create a new array with no reference to the first level.
   * 
   * Since, the items are not primitive, they get their own references. It means that any change on them,
   * it will be still reflected on the original object (aka arr1).
   */
  const arr2 = [...arr1];

  /**
   * Using Array.prototype.map() in conjunction Array.prototype.slice() will ensure:
   * - The first level is not a reference to the original array.
   * - In the second level, the items are forced (via slice()) to be created as new ones, so there is not reference to the original items
   */
  const arr3 = arr1.map(item => item.slice());

您需要了解要使用的阵列的复杂性,然后应用最佳解决方案(即➡️ 引用数组中的引用项)

其他回答

let a = [1,2,3];

现在,您可以执行以下任一操作来创建阵列的副本。

let b = Array.from(a); 

OR

let b = [...a];

OR

let b = new Array(...a); 

OR

let b = a.slice(); 

OR

let b = a.map(e => e);

现在,如果我改变一个,

a.push(5); 

那么,a是[1,2,3,5],但b仍然是[1,3,3],因为它有不同的引用。

但我认为,在上述所有方法中,Array.from都更好,并且主要用于复制数组。

这是我在尝试了许多方法之后所做的:

var newArray = JSON.parse(JSON.stringify(orgArray));

这将创建一个与第一个副本无关的新深度副本(而不是浅层副本)。

此外,这显然不会克隆事件和函数,但您可以在一行中完成它,并且它可以用于任何类型的对象(数组、字符串、数字、对象…)

在研究之后,我发现一个干净的方法可以是:

  const arr1 = [['item 1-1', 'item 1-2'], ['item 2-1', 'item 2-2'], ['item 3-1', 'item 3-2']];

  /**
   * Using Spread operator, it will create a new array with no reference to the first level.
   * 
   * Since, the items are not primitive, they get their own references. It means that any change on them,
   * it will be still reflected on the original object (aka arr1).
   */
  const arr2 = [...arr1];

  /**
   * Using Array.prototype.map() in conjunction Array.prototype.slice() will ensure:
   * - The first level is not a reference to the original array.
   * - In the second level, the items are forced (via slice()) to be created as new ones, so there is not reference to the original items
   */
  const arr3 = arr1.map(item => item.slice());

您需要了解要使用的阵列的复杂性,然后应用最佳解决方案(即➡️ 引用数组中的引用项)

您可以通过以下方式实现:arr2=arr1.map(x=>Object.assign({},x));

以下是如何对可变深度的基元数组执行此操作:

// If a is array: 
//    then call cpArr(a) for each e;
//    else return a

const cpArr = a => Array.isArray(a) && a.map(e => cpArr(e)) || a;

let src = [[1,2,3], [4, ["five", "six", 7], true], 8, 9, false];
let dst = cpArr(src);

https://jsbin.com/xemazog/edit?js安慰