These type of properties are not instance specific and are accessed by a class name instead of using the this keyword:

class Customer { 
     static bonusPercentage = 20; 
     constructor(public salary: number) {  } 
      calculateBonus() { 
          return this.salary * Customer.bonusPercentage/100; 
     } 
} 
var customer = new Customer(10000); 
var bonus = customer.calculateBonus(); 

Here, we declared a static variable, bonusPercentage, accessed using the Customer class name in the calculateBonus method. The bonusPercentage property is not instance specific.