exercise to check if input is object without using Equality operators or Object.is()

isObject.js

// exercise to check if input is object without using
// Equality operators or Object.is()
const isObject = (input) => {
  /******* Easiest Way ********/
  if (!input) return false;

  return !!(typeof input).match(/object|function/);

  /******* Longer Solution ********/

  if (!input) return false; // null or undefined

  // We can check by adding property to the input.
  // This works out since primitives are immutable
  // adding properties to primitives silently do nothing

  // prop happens to already exist in input
  if (input.hasOwnProperty("prop")) {
    return true;
  }

  input.prop = true;
  if (input.prop) {
    // input is successfully an object

    // however the input now has an extra key
    // our function must be pure and avoid side effects

    // remove prop key
    delete input.prop;
    return true;
  } else {
    return false;
  }
};

const objA = { whale: "🐋" };
const objB = { prop: "existing" };
const objC = {};
const arrA = ["🐋"];
const arrB = [];
const arrC = [];
arrB.prop = "existing";

console.log("hi", isObject("hi"));
console.log(true, isObject(true));
console.log(false, isObject(false));
console.log(null, isObject(null));
console.log(undefined, isObject(undefined));
console.log(NaN, isObject(NaN));
console.log(0, isObject(0));
console.log(5, isObject(5));
console.log(5n, isObject(5n));
console.log({}, isObject({}));
console.log([], isObject([]));
console.log(
  function () {},
  isObject(function () {})
);
console.log(objA, isObject(objA));
console.log(objB, isObject(objB));
console.log(objC, isObject(objC));
console.log(arrA, isObject(arrA));
console.log(arrB, isObject(arrB));
console.log(arrC, isObject(arrC));