Object.hasOwn()

const object1 = {
  prop: "exists",
};

console.log(Object.hasOwn(object1, "prop"));
//   : true

console.log(Object.hasOwn(object1, "toString"));
//   : false

console.log(Object.hasOwn(object1, "undeclaredPropertyValue"));
//   : false

Object.hasOwn(obj, prop)

const example = {};
Object.hasOwn(example, "prop"); // false - 'prop'  

example.prop = "exists";
Object.hasOwn(example, "prop"); // true - 'prop'  

example.prop = null;
Object.hasOwn(example, "prop"); // true -   null  

example.prop = undefined;
Object.hasOwn(example, "prop"); // true -   undefined  

const example = {};
example.prop = "exists";

// `hasOwn`     true .
Object.hasOwn(example, "prop"); // true
Object.hasOwn(example, "toString"); // false
Object.hasOwn(example, "hasOwnProperty"); // false

// `in`         true .
"prop" in example; // true
"toString" in example; // true
"hasOwnProperty" in example; // true

const example = { foo: true, bar: true };
for (const name of Object.keys(example)) {
  // 
}

const example = { foo: true, bar: true };
for (const name in example) {
  if (Object.hasOwn(example, name)) {
    // 
  }
}

const fruits = ["Apple", "Banana", "Watermelon", "Orange"];
Object.hasOwn(fruits, 3); // true ('Orange')
Object.hasOwn(fruits, 4); // false -  

const foo = {
  hasOwnProperty() {
    return false;
  },
  bar: "The dragons be out of office",
};

console.log(foo.hasOwnProperty("bar")); // false

console.log(Object.hasOwn(foo, "bar")); // true

const foo = Object.create(null);
foo.prop = "exists";

console.log(foo.hasOwnProperty("prop"));
// Uncaught TypeError: foo.hasOwnProperty is not a function

console.log(Object.hasOwn(foo, "prop")); // true