I'd write this as

let i=0;
for (; i < count && i < 2; i++) {
    arr.push(i + 1);
}
if (count > 4) {
    arr.push("…");
    i = count - 2;
}
for (; i < count; i++) {
    arr.push(i + 1);
}

You can predefine it in the if as well and then use the loop.

let arr =

 [];
const count = 10;

if (count <= 4) {
  for (let i = 0; i < count; i++) {
    arr.push(i);
  }
} else {
  arr = [1, 2, '...', count - 1, count];
}
console.log(arr);

JSFiddle

From what I see from the OP's expected outputs/results it looks like the problem was more about creating kind of a sequence with ellipsis. In this case one could choose a much simpler approach.

Any sequence with a count lower than and equal to 4 will be created via Array.from and its optional mapFn parameter. For any count value which exceeds 4 there is no necessity of using any kind of loop; just create an array with the first two items which are always 1 and 2, followed by the ellipsis placeholder of '...', followed by the last two items which always have the values of count - 1 respectively count.

function createEllipsisSequence(count) {
  let list;
  if (count <= 4) {

    list = Array
      .from({ length: count }, (_, idx) => idx + 1);
      
  } else {
    list = [1, 2, '...', count - 1, count];
  }
  return list;
}

console.log('count: 3 ...',
  createEllipsisSequence(3)
);
console.log('count: 4 ...',
  createEllipsisSequence(4)
);

console.log('count: 5 ...',
  createEllipsisSequence(5)
);
console.log('count: 6 ...',
  createEllipsisSequence(6)
);

console.log('count: 10 ...',
  createEllipsisSequence(10)
);
console.log('count: 11 ...',
  createEllipsisSequence(11)
);

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