方法一：使用数组的join()

let arr = [1, 2, 3, 4, 5, [6, 7, 8, [9, 10, 11, 12, [13, 14, 15, 16]]]]
console.log(arr.join())   // 输出为：1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16
let newArr = arr.join().split(',')
console.log(newArr) // 输出为：["1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16"]

方法二：使用toString()方法

let arr = [1, 2, 3, 4, 5, [6, 7, 8, [9, 10, 11, 12, [13, 14, 15, 16]]]]
console.log(arr.toString())   // 输出为：1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16
let newArr = arr.toString().split(',')
console.log(newArr)   // 输出为：["1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16"]

方法三： 使用空字符串的方法

let arr = [1, 2, 3, 4, 5, [6, 7, 8, [9, 10, 11, 12, [13, 14, 15, 16]]]]
console.log(arr + '')    // 输出为：1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16
let newArr = (arr + '').split(',')
console.log(newArr)   // 输出为：["1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16"]

优化 数组中每项为字符串将其转换成nunber类型 

let arr = [1, 2, 3, 4, 5, [6, 7, 8, [9, 10, 11, 12, [13, 14, 15, 16]]]]
console.log(arr + '')    // 输出为：1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16
let newArr = (arr + '').split(',')
console.log(newArr)   // 输出为：["1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16"]
let numberArr = [] // 用于存放新的number类型的数组
newArr.forEach(function (data, index, arr) {
  numberArr.push(+data)
})
console.log(numberArr) // 输出为：[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]

方法四：递归调用

let arr = [1, 2, 3, 4, 5, [6, 7, 8, [9, 10, 11, 12, [13, 14, 15, 16]]]]
let newArr = [] // 存放转化后的一维数组
function arrConversion (arr) {
  for (let i = 0; i < arr.length; i++) {
    if (Array.isArray(arr[i])) {
      arrConversion(arr[i])
    } else {
      newArr.push(arr[i])
    }
  }
}
arrConversion(arr)
console.log(newArr) // 输出：[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16]

const deepFlatten = arr => [].concat(...arr.map(v => (Array.isArray(v) ? deepFlatten(v) : v)));

deepFlatten([1, [2], [[3], 4], 5]); // [1,2,3,4,5]

方法五：flat()

console.log([1 ,[2, 3]].flat()); // [1, 2, 3]
 
// 指定转换的嵌套层数
console.log([1, [2, [3, [4, 5]]]].flat(2)); // [1, 2, 3, [4, 5]]
 
// 不管嵌套多少层
console.log([1, [2, [3, [4, 5]]]].flat(Infinity)); // [1, 2, 3, 4, 5]
 
// 自动跳过空位
console.log([1, [2, , 3]].flat());<p> // [1, 2, 3]

方法六： 正则

    let ary = [1, [2, [3, [4, 5]]], 6];
    let str = JSON.stringify(ary);
    let result = str.replace(/(\[|\])/g, '').split(',');
    console.log( result )

flatMap()

先对数组中每个元素进行了的处理，再对数组执行 flat() 方法。

// 参数1：遍历函数，该遍历函数可接受3个参数：当前元素、当前元素索引、原数组 // 参数2：指定遍历函数中 this 的指向 

// 参数1：遍历函数，该遍历函数可接受3个参数：当前元素、当前元素索引、原数组
// 参数2：指定遍历函数中 this 的指向
console.log([1, 2, 3].flatMap(n => [n * 2])); // [2, 4, 6]

方法六： 扩展运算符

let ary = [1, [2, [3, [4, 5]]], 6];// -> [1, 2, 3, 4, 5, 6]
//只要有一个元素有数组，那么循环继续
while (ary.some(Array.isArray())) {
  ary = [].concat(...ary);
}