Object.create()

Object.create() is a method that allows you to create a new object with a specified prototype object and optionally, additional properties.

Syntax

Object.create(proto);
Object.create(proto, propertiesObject);

Parameter

• proto: The object that will be the prototype of the newly created object.
• propertiesObject (optional): An object containing properties to be added to the newly created object. Each property descriptor is defined as a key-value pair. The key is the property name and the value is an object that describes the property.

If proto is null or undefined, Object.create() will create a new object with no prototype. The propertiesObject argument is optional. If it is not provided, the newly created object will have no properties other than those inherited from its prototype. propertiesObject can be used to define properties using property descriptors.

Return Value

Object.create() returns a new object with the specified prototype object and properties.

Examples

Example 1: Creating an object with a specified prototype

const animal = {
  type: "animal",
  describe() {
    console.log(`I am a ${this.type}.`);
  },
};

const dog = Object.create(animal);
dog.type = "dog";

dog.describe(); // Output: I am a dog.

Example 2: Creating an object with additional properties

const person = {
  firstName: "John",
  lastName: "Doe",
};

const employee = Object.create(person, {
  jobTitle: { value: "Software Developer" },
  salary: { value: 50000 },
});

console.log(employee.firstName); // Output: John
console.log(employee.jobTitle); // Output: Software Developer

Example 3: Creating an object without a prototype

const emptyObj = Object.create(null);
console.log(emptyObj.toString); // Output: undefined

Notes

• The prototype chain can be as long as you need it to be. You can create an object with a prototype, and then create another object with the first object as its prototype, and so on.

• The Object.create() method is often used in conjunction with the Object.defineProperty() method to create objects with specific properties and attributes.

• When using Object.create() to create an object with a prototype, any changes made to the properties of the prototype object will affect all objects that inherit from it.

• Object.create() is often used as an alternative to the new keyword and constructor functions for creating objects in JavaScript.

• Object.create() is more flexible than using the new keyword and constructor functions because it allows you to create objects with any prototype, not just those created by constructor functions.

Exercises

1. Create an object car with the properties make, model, and year using Object.create(). The make and model properties should be inherited from an vehicle object, and the year property should be set to the current year using the Date object.

2. Create an object person with the properties firstName, lastName, and age using Object.create(). The firstName and lastName properties should be inherited from a human object, and the age property should be set to the age of the person using the Date object and the person's birthdate.

3. Create an object student with the properties firstName, lastName, age, major, and gpa using Object.create(). The firstName, lastName, and age properties should be inherited from a person object, and the major and gpa properties should be set using propertiesObject.

fconst vehicle = {
  make: 'Toyota',
  model: 'Camry'
};

const car = Object.create(vehicle, {
  year: { value: new Date().getFullYear() }
});

console.log(car.make); // Output: Toyota
console.log(car.year); // Output: 2023

const human = {
  firstName: 'John',
  lastName: 'Doe'
};

const person = Object.create(human, {
  age: { value: () => {
    const birthdate = new Date('1990-01-01');
    const now = new Date();
    const diff = now - birthdate;
    const ageDate = new Date(diff);
    return Math.abs(ageDate.getUTCFullYear() - 1970);
  }}
});

console.log(person.firstName); // Output: John
console.log(person.age()); // Output: 33

const person = {
  firstName: 'John',
  lastName: 'Doe',
  age: 33
};

const student = Object.create(person, {
  major: { value: 'Computer Science' },
  gpa: { value: 3.8 }
});

console.log(student.firstName); // Output: John
console.log(student.major); // Output: Computer Science
console.log(student.gpa); // Output: 3.8