在 Javascript 中反转数组而不改变原始数组
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Reverse array in Javascript without mutating original array
提问by sfletche
Array.prototype.reversereverses the contents of an array in place (with mutation)...
Array.prototype.reverse原地反转数组的内容（带有突变）...
Is there a similarly simple strategy for reversing an array without altering the contents of the original array (without mutation)?
是否有类似的简单策略来反转数组而不改变原始数组的内容（没有突变）？
回答by Arun P Johny
回答by Brian M. Hunt
In ES6:
在 ES6 中：
const newArray = [...array].reverse()
回答by Mohammad Usman
Another ES6 variant:
另一个 ES6 变体：
We can also use .reduceRight()to create a reversed array without actually reversing it.
我们还可以使用.reduceRight()来创建一个反转数组，而无需实际反转它。
let A = ['a', 'b', 'c', 'd', 'e', 'f'];
let B = A.reduceRight((a, c) => (a.push(c), a), []);
console.log(B);Useful Resources:
有用的资源：
回答by Austin Keeton
Try this recursive solution:
试试这个递归解决方案：
const reverse = ([head, ...tail]) =>
tail.length === 0
? [head] // Base case -- cannot reverse a single element.
: [...reverse(tail), head] // Recursive case
reverse([1]); // [1]
reverse([1,2,3]); // [3,2,1]
reverse('hello').join(''); // 'olleh' -- Strings too!
回答by hanswilw
An ES6 alternative using .reduce()and spreading.
ES6 的替代使用.reduce()和传播。
const foo = [1, 2, 3, 4];
const bar = foo.reduce((acc, b) => ([b, ...acc]), []);
Basically what it does is create a new array with the next element in foo, and spreading the accumulated array for each iteration after b.
基本上它所做的是创建一个新数组，其中包含 foo 中的下一个元素，并在 b 之后为每次迭代扩展累积数组。
[]
[1] => [1]
[2, ...[1]] => [2, 1]
[3, ...[2, 1]] => [3, 2, 1]
[4, ...[3, 2, 1]] => [4, 3, 2, 1]
Alternatively .reduceRight()as mentioned above here, but without the .push()mutation.
或者.reduceRight()如上所述这里，但没有.push()突变。
const baz = foo.reduceRight((acc, b) => ([...acc, b]), []);
回答by shekhardtu
There are multiple ways of reversing an array without modifying. Two of them are
有多种方法可以在不修改的情况下反转数组。其中两个是
var array = [1,2,3,4,5,6,7,8,9,10];
// Using Splice
var reverseArray1 = array.splice().reverse(); // Fastest
// Using spread operator
var reverseArray2 = [...array].reverse();
// Using for loop
var reverseArray3 = [];
for(var i = array.length-1; i>=0; i--) {
reverseArray.push(array[i]);
}
Performance test http://jsben.ch/guftu
回答by Amit kumar
INTO plain Javascript:
INTO纯Javascript：
function reverseArray(arr, num) {
var newArray = [];
for (let i = num; i <= arr.length - 1; i++) {
newArray.push(arr[i]);
}
return newArray;
}
回答by daino3
Reversing in place with variable swap just for demonstrative purposes (but you need a copy if you don't want to mutate)
仅出于演示目的使用变量交换就地反转（但如果您不想变异，则需要一个副本）
const myArr = ["a", "b", "c", "d"];
const copy = [...myArr];
for (let i = 0; i < (copy.length - 1) / 2; i++) {
const lastIndex = copy.length - 1 - i;
[copy[i], copy[lastIndex]] = [copy[lastIndex], copy[i]]
}
回答by Radion Ponomarenko
es6:
es6：
const reverseArr = [1,2,3,4].sort(()=>1)
