freecodecamp上一道中级算法题

Question

能按照示例正确输出，为什么不通过？
题目链接

var res = [];

function steamroller(arr) {

  for(var i = 0; i < arr.length; i++){

    judge(arr[i]);

  }

  return res;

}

function judge(unknown){

  if(Array.isArray(unknown)){

    for(var i = 0; i < unknown.length;i++){

      judge(unknown[i]);

    }

  }else{

    res.push(unknown);

  }

}

steamroller([1, [], [3, [[4]]]]);

Answer 1

&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;function steamroller(arr) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; var res = [];&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; for(var i = 0; i < arr.length; i++){&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; judge(arr[i],res);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return res;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; function judge(unknown,res){&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if(Array.isArray(unknown)){&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; for(var i = 0; i < unknown.length;i++){&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; judge(unknown[i],res);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }else{&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; res.push(unknown);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }我试了试，他是需要4个条件同时满足