数组对角线输出

   var arr = [
              [1,2,3,4],
              [5,6,7,8],
              [9,10,11,12],
              [13,14,15,16]
            ];
    
    function outputArr(arr){
        var n = arr.length,
            newArr = [];
        for (var i = n - 1; i >= 0; i--) {  //右上角的三角形
            var temp = 0;
            for (var j = i; j < n; j++) {
                newArr.push(arr[temp++][j]);
            }
        }
        for (var i = 1; i < n; i++) {   //左下角的三角形
            var temp = 0;
            for (var j = i; j < n; j++) {
                newArr.push(arr[j][temp++]);
            }
        }
        return newArr;
    }
    console.log(outputArr(arr));  //[4, 3, 8, 2, 7, 12, 1, 6, 11, 16, 5, 10, 15, 9, 14, 13]