// 一,遞歸
        let arr = [1, [2, 3, 4, 5], [6, 7, 8, 9, [10, 11, 12, [14, 15, 16]]]] 
        let newArr = []
        const getArr=(array)=>{
            array.forEach((item)=>{
                // 如果遍歷的元素不是一個數(shù)組 就把這個元素放到新數(shù)組中 
                // 反之 就進行遞歸再次調用方法
                Array.isArray(item) ? getArr(item) : newArr.push(item)
            })
        }
        getArr(arr)
        console.log(newArr)

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

Array.prototype.flat()
let arr = [1, [2, 3, 4, 5], [6, 7, 8, 9, [10, 11, 12, [14, 15, 16]]]]
console.log(arr.flat(Infinity))

     var a = [1,[2],[3,4]]
     var result = []
     for(var i=0; i<a.length; i++){
        if(a[i].constructor == Array) {
            result = result.concat(a[i])
        }else {
            result.push(a[i])
        }
      }
      console.log(result)

    var a = [1,[2],[3,4]]
    var result = []
    result = [].concat(...a)
    console.log(result)