Static Methods and Properties

Static properties

The property that can be shared among all class instances is called static. we use static keywords to declare a static property. className.propertyName syntax is used to access the static property.

Example-

class Employee {
    static headcount: number = 0;


    constructor(
        private initialName: string,
        private lastName: string,
        private job: string) {


        Employee.headcount++;
    }
}

Here the static property headcount is initialized to 1, and whenever a new object is created headcount value is increased by 1.

now we are creating two objects to check the value of headocunt.

let mahinder = new Employee('Mahinder', 'singh', 'Front-end Developer');
let jugnu = new Employee('Jugnu', 'kaur', 'Back-end Developer');
let ram = new Employee('ram', 'kapoor', 'Back-end Developer');
console.log(Employee.headcount); // 3

This will return 3 as expected.

Output-

More examples

An example where a class contains a static member as well as a nonstatic member.

class Circle {
    static pi = 3.14;
    pi = 3.1;
}


Circle.pi; // returns 3.14


let circleObj = new Circle();
console.log(circleObj.pi); // returns 3.1

Output-

This example shows that static and non-static members can have the same name without showing any error. We use dot notation for accessing the static member, and for accessing the non-static member, we use the object.

LETS SEE ONE MORE EXAMPLE -

class Circle {
    static pi = 3.14;


    static calculateArea(radius:number) {
        return this.pi * radius * radius;
    }


    calculateCircumference(radius:number):number { 
        return 2 * Circle.pi * radius;
    }
}


console.log(Circle.calculateArea(5)); // returns 78.5

Output-

let circleObj = new Circle();
console.log(circleObj.calculateCircumference(5)); // returns 31.4000000

Output-

//circleObj.calculateArea(); <-- cannot call this

In this example, we have a class containing a static method that includes both static and non-static members, which are calculateArea and calculateCircumference. Here we access the static field pi with this.pi in the static method, and we use Circle.pi for accessing the non-static (instance) method.

Frequently Asked Questions

1.Does typescript have static classes?

No, typescript doesn't have static classes and there is no need for them. 

2.Can we access Static members by object instance?

Typescript does not allow a static property or method to be affected by an object instance, therefore, we cannot access the static members by the object instance.

Key Takeaways

In this blog, we learned about Static Methods and Properties. Don't come to a halt here. Check out our Typescript vs Javascript: Learn the difference | Coding Ninjas Blog. Can you also check out the TypeScript Interview Questions | Part 1 | Coding Ninjas Blog blog? Check out more blogs here. More Blogs.