Run results for: Flatten arrays

Run details:

User agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/60.0.3112.101 Safari/537.36

Browser: Chrome 60

Operating system: Windows

Device Platform: Other

Date tested: 6 years ago

Test name	Executions per second
flatten1	0.0 Ops/sec
flatten1 - true	0.0 Ops/sec
flatten2	684895.9 Ops/sec
flatten2 - true	279542.5 Ops/sec

Script Preparation code:

var a = [1,[2,3,[[4,5],[[6]]]],7];
var flatten1 = function(input, shallow, strict, output) {
  output = output || [];
  var idx = output.length;
  for (var i = 0, length = getLength(input); i < length; i++) {
    var value = input[i];
    if (isArrayLike(value) && (_.isArray(value) || _.isArguments(value))) {
      // Flatten current level of array or arguments object.
      if (shallow) {
        var j = 0, len = value.length;
        while (j < len) output[idx++] = value[j++];
      } else {
        flatten1(value, shallow, strict, output);
        idx = output.length;
      }
    } else if (!strict) {
      output[idx++] = value;
    }
  }
  return output;
};
function flatten2(arr, shallow = false) {
  return arr.reduce(function (flat, toFlatten) {
    return flat.concat(shallow && Array.isArray(toFlatten) ? flatten2(toFlatten) : toFlatten);
  }, []);
}

Tests:

flatten1
flatten1(a);
flatten1 - true
flatten1(a, true);
flatten2
flatten2(a);
flatten2 - true
flatten2(a,true);

Run results for: Flatten arrays

flatten1

flatten1 - true

flatten2

flatten2 - true