Static members

Learn class-level members with static.

What is static?

Members defined with static belong to the class itself, not to instances. They are accessed directly with the class name, without creating an instance. For example MathUtil.PI and MathUtil.square(5).

class MathUtil {
  static PI: number = 3.14;
  static square(n: number): number {
    return n * n;
  }
}
console.log(MathUtil.PI);
console.log(MathUtil.square(5));

Instance vs static

Instance members are accessed after creating an instance with new, while static members are accessed directly with the class name. To access a static field from inside an instance method, you use the class name.

class Counter {
  static count: number = 0;
  increment(): void {
    Counter.count++;
  }
}

Exercise Write a Counter class

Define a Counter class. Add a static count: number = 0 field and a static increment(): void method (the method increments Counter.count). Call Counter.increment() twice and print Counter.count.

Show example solution

class Counter {
  static count: number = 0;
  static increment(): void {
    Counter.count++;
  }
}

Counter.increment();
Counter.increment();
console.log(Counter.count);

Test yourself

How is a static member accessed?
- First create an instance with new
- Directly with the class name
- With super.
- With this.
Show answer

Directly with the class name — Static members are accessed directly with the class name without creating an instance: MathUtil.PI. this and super are used in an instance context; new creates an instance.

Complete the static keyword

class MathUtil {
  ____ PI: number = 3.14;
}

Show answer

class MathUtil {
  static PI: number = 3.14;
}

Static member parts

static

Class-level member
MathUtil.PI

Static field access
MathUtil.square(5)

Static method call
Counter.count

Access via class name

Next lesson: Summary - Classes

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