function stray_happy(numbers) {

  numbers = numbers.sort((a, b) => a - b);

  if (numbers[0] !== numbers[1]) {

    return numbers[0];

  }

  else {

    return numbers[numbers.length - 1];

  }

}

​

​

function stray_heretic(numbers) {

  return numbers.find(i => numbers.filter(j => j === i).length === 1);

}

​

​

function stray_shaye(numbers) {

  return +numbers.sort((a, b) => a - b)

    .filter((n,i,a) => (i === 0 && a[0] !==a[1]) || (i === a.length-1 && a[a.length-1] !== a[a.length-2]));

}

​

function stray_user(a) {

  return a.find(v => a[0] != a[1] ? v != a[2] : v != a[0])

}

​

function stray_user_2(a) {

    a.find(a[0] != a[1] ? (v, i, a) => v != a[2] : (v, i, a) => v != a[0])

}

​

​

function stray_user_3(a) {

    var a0 = a[0], a1 = a[1], a2 = a[2];

    a.find(a0 != a1 ? (v, i, a) => v != a2 : (v, i, a) => v != a0)

}

​

function stray_user_4(a) {

    var a0 = a[0], a1 = a[1], a2 = a[2];

    if (a0 != a1) a.find((v,i,a) => v != a2);

    else a.find((v,i,a) => v != a0);

}

​

​

var numbers = [1,1,1,1,1,1,1,2,1,1,1,1,1,1,1]

​

​