Best practice to convert multidimensional array to flat array of objects in ES6

Question

I have a source multidimensional array. It looks like:

var arr = [];
arr[1] = [];
arr[2] = [];
arr[3] = [];
arr[1][1] = "11";
arr[1][2] = "12";
arr[1][3] = "13";
arr[2][1] = "21";
arr[2][2] = "22";
arr[2][3] = "23";
arr[3][1] = "31";
arr[3][2] = "32";
arr[3][3] = "33";

I need to convert this to a flat array using ES6 features. Result must looks like this:

var res = [
  { col:1, row:1, val:"11"},
  { col:1, row:2, val:"12"},
  { col:1, row:3, val:"13"},
  { col:2, row:1, val:"21"},
  { col:2, row:2, val:"22"},
  { col:2, row:3, val:"23"},
  { col:3, row:1, val:"31"},
  { col:3, row:2, val:"32"},
  { col:3, row:3, val:"33"}
];

Answer 1

You could use Array#reduce and Array#forEach for new objects.

 var arr = [, [, '11', '12', '13'], [, '21', '22', '23'], [, '31', '32', '33']], result = arr.reduce((r, a, col) => (a.forEach((val, row) => r.push({ col, row, val })), r), []); console.log(result); 

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