JavaScript classes and object
JavaScript class-
JavaScript classes, introduced in ES6 (ECMAScript 2015),
provide a more structured and object-oriented way to create objects with shared properties and methods, acting as templates JavaScript arrayor blueprints.
JavaScript Classes are templates for JavaScript Objects.
JavaScript Class Syntax
Use the keyword class to create a class.
Always add a method named constructor():
Syntax
class ClassName {
constructor() { ... }
}
Example
class Car {
constructor(name, year) {
this.name = name;
this.year = year;
}
}
Using a Class
When you have a class, you can use the class to create objects:
Example -
const myCar1 = new Car("Ford", 2014);
const myCar2 = new Car("Audi", 2019);
The Constructor Method
The constructor method is a special method:
- It has to have the exact name "constructor"
- It is executed automatically when a new object is created
- It is used to initialize object properties
If you do not define a constructor method, JavaScript will add an empty constructor method.
Class Methods
Class methods are created with the same syntax as object methods.
Use the keyword class to create a class.
Always add a constructor() method.
Then add any number of methods.
Syntax
class ClassName {
constructor() { ... }
method_1() { ... }
method_2() { ... }
method_3() { ... }
}
Example
<!DOCTYPE html>
<html>
<body>
<h1>JavaScript Class Methods</h1>
<p>How to define and use a Class method.</p>
<p id="demo"></p>
<script>
class Car {
constructor(name, year) {
this.name = name;
this.year = year;
}
age() {
const date = new Date();
return date.getFullYear() - this.year;
}
}
const myCar = new Car("Ford", 2014);
document.getElementById("demo").innerHTML =
"My car is " + myCar.age() + " years old.";
</script>
JavaScript Class Methods
How to define and use a Class method.
My car is 11 years old.
Object
An object in JavaScript is a specific instance of a class. It contains its own set of data (properties) and can use the methods defined in its class. Multiple objects can be created from the same class, each having unique values for their properties.
JavaScript Object Properties
In JavaScript the members inside the object which are the key: values are called Object properties. For example, in the above code, name is an object property (unique to each instance), and sound is a class property (shared by all instances of the class).
To Access Object Properties:
1. Using dot Notation:
Syntax:
object_name.key_12. Using bracket Notation:
Syntax:
object_name["key_1"]JavaScript Nested Objects: In this case, an object contains another object inside it.
Example:
JavaScript Object Methods
In JavaScript, we can add methods to Objects.
Example: In the given example we can see how we can apply Javascript nested objects and also use the different accessing methods.
Output:
Husky
18 inches
Gray & White
30 pounds
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