关于javascript:数组扁平化

办法一：递归

var arr3 = [1,[2,3],[2,[1,3]],[[2,4],[2,8]]]

function flaten(arr){let result = [];
    arr.forEach((item)=>{if(Array.isArray(item)){result = result.concat(flaten(item))
        }else{result.push(item)  
        }
    })
    return result
}

console.log(flaten(arr3))

办法二：reduce+ 递归

function flatenReduce (arr){return arr.reduce((res,item)=>{return res.concat(Array.isArray(item)?flatenReduce(item):item)
    },[])
}

console.log(flatenReduce(arr3))