Javascript Range Syntax

main.js

const checkValidRangeSyntax = (arr) => {
  if (arr.length !== 4) {
    return false;
  }
  if (Object.keys(arr).length !== 2) {
    return false;
  }
  const start = arr[0];
  const end = arr[3];
  if (!Number.isInteger(start) || !Number.isInteger(end)) {
    return false;
  }

  return end > start;
};
const makeRangeArray = (arr) => {
  const start = arr[0];
  const end = arr[3];
  const result = [];

  for (let i = start; i < end; i++) {
    result.push(i);
  }

  return result;
};


[Symbol.iterator, "map", "forEach"].forEach((name) => {
  const originMethod = Array.prototype[name];

  Array.prototype[name] = function (...args) {
    const target = checkValidRangeSyntax(this) ? makeRangeArray(this) : this;
    return originMethod.apply(target, args);
  };
});


console.log("Normal Array:");
for (let item of [1, 2, 3, 4]) {
  console.log(item);
}
console.log([1, 2, 3, 4].map((item) => item));

console.log("Range Array:");
for (let item of [1, , , 5]) {
  console.log(item);
}
console.log([1, , , 5].map((item) => item));