16 一维数组变成二维数组

<script>
        // 将数组分成三个
        var arr = [1,2,3,4,5,6,7,8,9];
        var test = [];
        for(var i=0;i<arr.length;i+=3){
            test.push(arr.slice(i,i+3));
        }
        console.log(test);
    </script>