TypeScript Modifiers
The TypeScript supports to multiple modifiers and it is by default public.
1. Public,
2. Private,
3. Protected and
4. Read-only
Public by default! Stayed Informed – Learn Angular 2 with TypeScript
Public Modifier – Public by default! It is freely access anywhere.
In the below example, the class Employee and its members are by default public and we are freely access it.
Example –
class Employee {
empName: string;
constructor(name: string) {
this.empName = name;
}
salary(salary: number = 10000) {
console.log('Hello, ' + this.empName + ' Your Salary -' + salary);
}
}
let empSal = new Employee("Anil");
console.log(empSal.salary());
console.log(empSal.salary(40000));
Private Modifier -When using private modifier, we can’t be accessed from outside of its containing class.
class Employee {
private empName: string;
constructor(name: string) {
this.empName = name;
}
salary(salary: number = 10000) {
console.log('Hello, ' + this.empName + ' Your Salary -' + salary);
}
}
let emp = new Employee("Anil").empName;
//error: property 'empName' is private and only accesible in the class 'Employee'.
Protected Modifier - The protected modifier is very similar to private but only one difference that can be accessed by instances of deriving classes.
Example as,
class Employee {
protected empName: string;
constructor(name: string) {
this.empName = name;
}
salary(salary: number = 10000) {
console.log('Hello, ' + this.empName + ' Your Salary -' + salary);
}
}
class Employer extends Employee {
private department: string;
constructor(empName: string, department: string) {
super(empName);
this.department = department;
}
salary(salary = 20000) {
super.salary(salary);
}
}
let empSal = new Employer("Anil", "IT");
console.log(empSal.salary());
console.log(empSal.empName); //error- the property 'empName' is protected and only accesible within the class 'Employee' and its child class.
Readonly Modifier - Read-only properties must be initialized at their declaration or in the constructor.
For example as,
class Employee {
readonly empName: string;
constructor(name: string) {
this.empName = name;
}
salary(salary: number = 10000) {
console.log('Hello, ' + this.empName + ' Your Salary -' + salary);
}
}
let emp = new Employee('Anil');
emp.empName = 'Anil Singh';//error - cannot assign to 'empName' because it is constant or readonly.
Stayed Informed – Learn Angular 2 with TypeScript
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