不懂就问，请问组数怎么每隔N长度做倒序

Question

比如间隔3个长度倒序

[1,2,3,4,5,6,7,8,9] => [3,2,1,6,5,4,9,8,7]

Answer 1

什么业务场景要这样使用呢?

应该没有原生函数直接做这个事情吧,比较直接的就是直接把数组拆成符合你的 N 的小数组,倒序后合并.

或者,使用 for 来循环数组,通过索引的方式对数组快速的倒序.

Answer 2

const ary = [1, 2, 3, 4, 5, 6, 7, 8, 9];
const result = Array.from(
  {length: Math.ceil(ary.length / 3)},
  (v, i) => ary.slice(i * 3, (i + 1) * 3).sort((a, b) => b - a),
).flat();

把原数组按3分割后排序，再合并起来。
效率肯定比不上一个个循环处理，但胜在逻辑清晰，代码易读

Answer 3

2层循环，第一层步长是间隔数量，比如例子就是3.

function reverseByStep(l, step) {
    for (let i = 0; i < l.length; i = i + step) {
        let j = i, k = Math.min(l.length, i + step) - 1
        while (j < k) {
            [l[j], l[k]] = [l[k], l[j]]
            j++
            k--
        }
    }
    return l
}

Answer 4

 function ss(d) {
        var arr = [1, 2, 3, 4, 5, 6, 7, 8, 9];
        var arr2 = []
        var num = Math.ceil(arr.length / d);
        for (var i = 0; i < num; i++) {
            arr2.push(...arr.slice(0, d).reverse())
            arr.splice(0, d)
        }
        console.log(arr2)
    }
    ss(2)

Answer 5

function group(array, key) {
    var index = 0;
    var newArray = [];
    // 先切成二维数组
    while (index < array.length) {
        newArray.push(array.slice(index, index += key));
    }
    // 把二维数组倒叙
    newArray.map(v=> v.reverse())
    // 去除二维数组
    return newArray.reduce((prev, curr) => (prev.concat(curr)), []);;
}
var countries = [1, 2, 3, 4, 5, 6, 7, 8, 9];
var groupedCountries = group(countries, 3);
console.log(groupedCountries)

Answer 6

const l = [1, 2, 3, 4, 5, 6, 7, 8, 9]

function arrayReverse(l, num) {
  let temp_l = []
  for (let i = 0; i < Math.ceil(l.length / num); i++) {
    const startIndex = i * num
    temp_l = temp_l.concat(l.slice(startIndex, startIndex + num).reverse())
  }
  return temp_l
}

console.log(arrayReverse(l, 3))
// 输出
//[3, 2, 1, 6, 5, 4, 9, 8, 7]

Answer 7

console.log(splitReverseArr([1,2,3,4,5,6,7,8,9,10],3))

function splitReverseArr(arr,number){
    let len = Math.ceil(arr.length/3)
    let index = 0
    let res = []
    while(index < len){
        // res = res.concat(arr.slice(index*number,(index*number)+number).reverse())
        res = res.concat(arr.splice(0,number).reverse())
        index++
    }
    return res
}