扩展语法如何影响数组拼接 [英] How does the spread syntax affect array splice

问题描述

我发现以下代码，我不知道A和B之间有什么区别：

I found the following code and I don't know what is the difference between A and B:

var fruits = ["Banana", "Orange", "Apple", "Mango"];

A

fruits.splice(2,0,["Lemon", "Kiwi"]);

B

fruits.splice(...[2,0].concat(["Lemon", "Kiwi"]));

var fruits = ["Banana", "Orange", "Apple", "Mango"];
var A = fruits.splice(2, 0, ["Lemon", "Kiwi"]);
var B = fruits.splice(...[2, 0].concat(["Lemon", "Kiwi"]));

console.log(A)
console.log(B)

推荐答案

首先，声明A&声明B将生成不同的结果。

First of all, Statement A & Statement B will generate different results.

在语句A 中，您正在插入一个数组（ [Lemon， Kiwi] ）作为位置2的数组元素，同时删除0个项目。所以，你在一个位置2的另一个字符串数组中插入一个字符串数组。

In Statement A, you are inserting an array (["Lemon", "Kiwi"]) as an array element at position 2 while removing 0 items. So, you are inserting a string array in another string array at position 2.

var fruits = ["Banana", "Orange", "Apple", "Mango"];


fruits.splice(2,0,["Lemon", "Kiwi"]);

console.log(fruits);

然而，声明B 更有趣。为了完全理解它，首先注销它的核心部分如下：

However, Statement B is much more interesting. To, understand it fully, first log out it's core portion like this:

console.log(...[2,0].concat(["Lemon", "Kiwi"]));  // basic array concatenation then spread

正如你所看到的那样生成， 2 0柠檬奇异果。然后它作为参数传递给 fruits.splice（.. here ..）。根据 array＃splice 它将在第2位输入两个字符串（Lemon& Kiwi），同时删除0个元素。

As you can see it generates, 2 0 Lemon Kiwi. Then it is passed as parameter to fruits.splice(..here..). According to array#splice it will enter two strings (Lemon & Kiwi) at position 2, while removing 0 elements.

var fruits = ["Banana", "Orange", "Apple", "Mango"];

fruits.splice(...[2,0].concat(["Lemon", "Kiwi"]));
// is same as fruits.splice(2, 0, 'Lemon', 'Kiwi')

console.log(fruits);

注意：

• array＃splice 更新原始数组。


• 声明A 插入 数组 （IE [父字符串数组中的Lemon，Kiwi] ），而语句B 插入两个字符串（IE 'Lemon'，'Kiwi'）在父字符串数组中。

• array#splice updates the original array.
• Statement A inserts an array (IE ["Lemon", "Kiwi"]) in parent string array whereas, Statement B inserts two strings (IE 'Lemon', 'Kiwi') in parent string array.

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