將多維數組轉換為一維數組
解決方案有很多，以下來一一例舉
方法一：使用數組的join()
let arr = [1, 2, 3, 4, 5, [6, 7, 8, [9, 10, 11, 12, [13, 14, 15, 16]]]]
console.log(arr.join()) // 輸出為：1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16
let newArr = arr.join().split(',')
console.log(newArr) // 輸出為：["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()) // 輸出為：1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16
let newArr = arr.toString().split(',')
console.log(newArr) // 輸出為：["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+ '') // 輸出為：1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16
let newArr = (arr+ '').split(',')
console.log(newArr) // 輸出為：["1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16"]
方法四：遞歸調用
let arr = [1, 2, 3, 4, 5, [6, 7, 8, [9, 10, 11, 12, [13, 14, 15, 16]]]]
let newArr = [] // 存放轉化后的一維數組
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) // 輸出為：["1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16"]
es6寫法
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]
// 指定轉換的嵌套層數
console.log([1, [2, [3, [4, 5]]]].flat(2)); // [1, 2, 3, [4, 5]]
// 不管嵌套多少層
console.log([1, [2, [3, [4, 5]]]].flat(Infinity)); // [1, 2, 3, 4, 5]
// 自動跳過空位
console.log([1, [2, , 3]].flat()); // [1, 2, 3]
方法六： 正則
let ary = [1, [2, [3, [4, 5]]], 6];
let str = JSON.stringify(ary);
let result = str.replace(/(\[|\])/g, '').split(',');
console.log(result)
方法七： 擴展運算符
let ary = [1, [2, [3, [4, 5]]], 6];// -> [1, 2, 3, 4, 5, 6]
//只要有一個元素有數組，那么循環繼續
while (ary.some(Array.isArray())) {
ary = [].concat(...ary);
}