SOURCE

//           数组扁平化
//1、递归实现
function flatten(arr){
    let result=[]
    for(item of arr){
        if(Array.isArray(item)){
            result=result.concat(flatten(item))
        }else{
            result.push(item)
        }
    }
    return result
}

//2、flat实现

function flatten4(arr) {
	return arr.flat(Infinity)
}
//扩展运算符



















const numArr=[4,32,[22,1,3],45,[[1,91],1]]

console.log('递归'+flatten(numArr))
console.log('flat'+flatten4(numArr))
console.log('---------')