Javascript - Sorting on two (specific) types (slow & fast)

fastSort.js

//SLOW
const arr = [
  { flag: true, other: 1 },
  { flag: true, other: 2 },
  { flag: false, other: 3 },
  { flag: true, other: 4 },
  { flag: true, other: 5 },
  { flag: true, other: 6 },
  { flag: false, other: 7 }
];

new Array(11).fill().forEach(x => arr.push(...arr));

console.time();

const reducedArr = arr.reduce((acc, element) => {
  if (element.flag === false) {
    return [element, ...acc];
  }
  return [...acc, element];
}, []);

console.timeEnd(); // RESULTS: between 285-350ms

//FAST
const arr = [
  { flag: true, other: 1 },
  { flag: true, other: 2 },
  { flag: false, other: 3 },
  { flag: true, other: 4 },
  { flag: true, other: 5 },
  { flag: true, other: 6 },
  { flag: false, other: 7 }
];

new Array(11).fill().forEach(x => arr.push(...arr));

console.time();

const rebuiltArray = [
  ...arr.filter(x => !!x.flag),
  ...arr.filter(x => !x.flag)
];

console.timeEnd(); // RESULTS: between 6-20ms