Constructor method
- In JavaScript, a constructor method is used to create and initialize objects.
- In object-oriented programming, Constructors are used to define and create objects of a particular class or type.
- They are called when you use the new keyword to create an instance of an object.
Syntax:
function ClassName(param1, param2, ...) {
// Constructor code here
// Initialize instance properties
this.param1 = param1;
this.param2 = param2;
// ...
}
- ClassName is the name of the constructor function.
- param1, and param2, are parameters that you can pass to the constructor when creating an instance of the object.
- this refers to the newly created instance of the object, and you can use it to set instance properties.
Example:
<!DOCTYPE html>
<html>
<body>
<script>
class Employee {
constructor() {
this.id = 105;
this.name = "john";
}
}
var emp = new Employee();
document.writeln(emp.id + " " + emp.name);
</script>
</body>
</html>
Output:
105 john
Using super keyword:
- super keyword is used to call parent class Constructor.
Example:
<!DOCTYPE html>
<html>
<body>
<script>
class CompanyName {
constructor() {
this.company = "Quipoin";
}
}
class Employee extends CompanyName {
constructor(id, name) {
super();
this.id = id;
this.name = name;
}
}
var emp = new Employee(1, "John");
document.writeln(emp.id + " " + emp.name + " " + emp.company);
</script>
</body>
</html>
Output:
1 John Quipoin