if (typeof objectName.propertyName === "undefined") {
    // Do something if the property is undefined
}

const obj = { prop1: 'value1' };
if (typeof obj.prop2 === 'undefined') {
    console.log('prop2 is undefined');
};

const car = { 
    make: "Toyota", 
    model: "Camry", 
    year: 2018 
}; 
  
if (typeof car.color === "undefined") { 
    console.log("The color property is undefined in the car object."); 
} 
else { 
    console.log("The color property is defined in the car object."); 
}

The color property is undefined in the car object.

const obj = { prop1: 'value1' };
if (!('prop2' in obj)) {
    console.log('prop2 is undefined');
};

const book = { 
    title: "The Great Gatsby", 
    author: "F. Scott Fitzgerald", 
    pages: 218 
}; 
  
if ("publisher" in book) { 
    console.log("The publisher property exists in the book object."); 
} 
else { 
    console.log("The publisher property does not exist in the book object."); 
}

The publisher property does not exist in the book object.

const obj = { prop1: 'value1' };
if (!obj.hasOwnProperty('prop2')) {
    console.log('prop2 is undefined');
}

const person = { 
    firstName: "John", 
    lastName: "Doe", 
    age: 30 
}; 
  
console.log(person.hasOwnProperty("firstName")); // true 
console.log(person.hasOwnProperty("middleName")); // false 

true
false

const obj = { prop1: 'value1' };
if (obj.prop2 === undefined) {
    console.log('prop2 is undefined');
}

const superHero = { 
    name: 'Batman'
}; 
console.log(superHero.name !== undefined); 
console.log(superHero.realName !== undefined);

true
false