Explain JavaScript Object Methods

JavaScript object methods are functions that are stored as object properties. These methods can perform actions using the data contained in the object. Let's go over some common object methods with examples:

1. Creating an Object with Methods

const person = {
  firstName: "John",
  lastName: "Doe",
  age: 30,
  fullName: function() {
    return this.firstName + " " + this.lastName;
  },
  greet: function() {
    return "Hello, " + this.firstName;
  }
};

console.log(person.fullName()); // Output: John Doe
console.log(person.greet()); // Output: Hello, John

2. Using this Keyword

The this keyword refers to the object that the method is a property of. In the above example, this.firstName refers to person.firstName.

3. Adding Methods to an Existing Object

You can also add methods to an object after it has been created:

const car = {
  make: "Toyota",
  model: "Corolla",
  year: 2020
};

car.getCarInfo = function() {
  return this.make + " " + this.model + " (" + this.year + ")";
};

console.log(car.getCarInfo()); // Output: Toyota Corolla (2020)

4. Object Methods with Parameters

Methods can also take parameters:

const calculator = {
  add: function(a, b) {
    return a + b;
  },
  subtract: function(a, b) {
    return a - b;
  }
};

console.log(calculator.add(5, 3)); // Output: 8
console.log(calculator.subtract(9, 4)); // Output: 5

5. Built-in Object Methods

JavaScript provides several built-in methods for objects. Some of these include:

• Object.keys()
• Object.values()
• Object.entries()

Object.keys()

Returns an array of a given object's own enumerable property names.

const user = {
  name: "Alice",
  age: 25,
  city: "Wonderland"
};

console.log(Object.keys(user)); // Output: ["name", "age", "city"]

Object.values()

Returns an array of a given object's own enumerable property values.

console.log(Object.values(user)); // Output: ["Alice", 25, "Wonderland"]

Object.entries()

Returns an array of a given object's own enumerable property [key, value] pairs.

console.log(Object.entries(user)); // Output: [["name", "Alice"], ["age", 25], ["city", "Wonderland"]]

6. this Inside Methods

When a method is called as a property of an object, this refers to the object itself.

const book = {
  title: "1984",
  author: "George Orwell",
  getSummary: function() {
    return `${this.title} by ${this.author}`;
  }
};

console.log(book.getSummary()); // Output: 1984 by George Orwell

Conclusion

JavaScript object methods are essential for creating and manipulating objects effectively. They provide a way to bundle related data and behavior, making your code more modular and easier to understand.