Merging many arrays from Promise.all

ES2019 introduced Array.prototype.flat which significantly simplifies this to:

const nums = data.flat();

const data = [
  [ 1, 4, 9, 9 ],
  [ 4, 4, 9, 1 ],
  [ 6, 6, 9, 1 ]
];

const nums = data.flat();

console.log(nums);

_{Original Answer}

Use reduce and concat:

data.reduce(function (arr, row) {
  return arr.concat(row);
}, []);

Or alternatively, concat and apply:

Array.prototype.concat.apply([], data);

I would do as follows;

var a = [
    [ 1, 4, 9, 9 ],
    [ 4, 4, 9, 1 ],
    [ 6, 6, 9, 1 ]
],
    b = [].concat(...a)

console.log(b)

Related