Run results for: Array Flatten -> Reduce+Concat | Reduce+Spread | Loop+Push| Loop+Push+Spread

Run details:

User agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.100 Safari/537.36

Browser: Chrome 69

Operating system: Mac OS X 10.13.4

Device Platform: Desktop

Date tested: 5 years ago

Test name	Executions per second
Reduce+Concat	885572.0 Ops/sec
Reduce+Spread	1465812.0 Ops/sec
Loop+Push	2622097.0 Ops/sec
Loop+Push+Spread	2027551.0 Ops/sec
Loop+Spread	1467300.0 Ops/sec

Script Preparation code:

var params = [ [ 1, 2 ], [ 3, 4 ], [ 5, 6 ], [ 7, 8 ], [ 9, 0 ] ];

var flattenReduceConcat = (inputs) => inputs.reduce((acc, input) => acc.concat(input), []);
var flattenReduceSpread = (inputs) => inputs.reduce((acc, input) => [...acc, ...input], []);
var flattenLoopPush = (inputs) => {
  var acc = [];
  for (var i = 0, L = inputs.length; i < L; i++) {
    var input = inputs[i];
    for (var j = 0, l = input.length; j < l; j++) {
      acc.push(input[j]);
    }
  }
  return acc;
}
var flattenLoopPushSpread = (inputs) => {
  var acc = [];
  for (var i = 0, l = inputs.length; i < l; i++) {
    acc.push(...inputs[i]);
  }
  return acc;
}
var flattenLoopSpread = (inputs) => {
  var acc = [];
  for (var i = 0, l = inputs.length; i < l; i++) {
    acc = [...acc, ...inputs[i]];
  }
  return acc;
}

Tests:

Reduce+Concat
var result = flattenReduceConcat(params);
Reduce+Spread
var result = flattenReduceSpread(params);
Loop+Push
var result = flattenLoopPush(params);
Loop+Push+Spread
var result = flattenLoopPushSpread(params);
Loop+Spread
var result = flattenLoopSpread(params);

Run results for: Array Flatten -> Reduce+Concat | Reduce+Spread | Loop+Push| Loop+Push+Spread | Loop+Spread

Reduce+Concat

Reduce+Spread

Loop+Push

Loop+Push+Spread

Loop+Spread