Реализация метода пуш

numbers.push = function(number) {
  if (number === undefined) {
    return this.length;
  }
  this[this.length] = number;
 
  const count = this.length;
 
  return count;
};

Array.prototype.JuliusCaesarPush = function (...elems) {
    for(let e of elems) this[this.length] = e;
    return this.length;
};
 
const arr = ['однажды'];
 
console.log(arr.JuliusCaesarPush('в', 'студёную', 'зимнюю', 'пору')); // 5
console.log(arr); // ['однажды', 'в', 'студёную', 'зимнюю', 'пору']

Array.prototype.JuliusCaesarPush = function (...elems) {
  for (let e of elems) this[this.length] = e;
  return this.length;
};
 
const test1 = { length: "a" };
const test2 = { length: "a" };
Array.prototype.JuliusCaesarPush.call(test1, 1);
console.log(test1); // {length: "a", a: 1}
Array.prototype.push.call(test2, 1);
console.log(test2); // {length: 1, 0: 1}

let a = [];
a = [...a, ...['полковнику', 'никто', 'не', 'пишет']];
console.log(a);

const t1 = { length: "5" };
const t2 = { length: [10] };
Array.prototype.push.call(t1, 333); // Object { 5: 333, length: 6 }
Array.prototype.push.call(t2, 444); // Object { 10: 444, length: 11 }

const t1 = { length: "5" };
Array.prototype.push.apply(t1, [1, 2, 3, 4, 5]); // { 5: 1, 6: 2, 7: 3, 8: 4, 9: 5, length: 10 }

const t1 = { length: "5" };
Array.prototype.push.apply(t1, [1, 2, 3, 4, 5]);
 
console.log(Array.from(t1)); // [undefined, undefined, undefined, undefined, undefined, 1, 2, 3, 4, 5]
console.log([...t1]); // Uncaught TypeError: t1 is not iterable

t1[Symbol.iterator] = function* () {
    const v = Object.values(o);
    yield v;
  };