Map Diagonal

gistfile1.txt

function mapDiagonal(arr){

    var row_mapper = Array.from({length: arr.length}, (v, i) => i),
        col_mapper = Array.from({length: arr[0].length}, (v, i) => i),
        _mapper = row_mapper.map(val => col_mapper.map(_val => [val,_val]));

        _mapper = _mapper.reduce((acc,cur)=>{
            acc = acc.concat(cur)
            return acc;
          }, [])
          .reduce((acc,cur)=>{
            if(acc[cur[0] + cur[1]]){
              acc[cur[0] + cur[1]].push(cur)
            } else {
              acc[cur[0] + cur[1]] = [cur];
            }
            return acc;
          }, {})

     return _mapper;

}

var orig_arr = [
    [1,2,3,4,5],
    [6,7,8,9,10],
    [11,12,13,14,15]
];

var mapped = mapDiagonal(orig_arr);

mapped = Object.keys(mapped).reverse().map(key => {
  var print = mapped[key].map((val) => {
    return orig_arr[val[0]][val[1]];
  })
  console.log(print)
  return print;
})