ES13 introduced public and private properties like other programming languages. ES06 introduced classes to javascript, fields or properties initialized in the constructor

Fields initilized in the constructor using this keyword before ES13.

In the below example, the Employee class has three fields id, name, and salary and initilized in constructor using this.

class Employee  {
  
  constructor() {
    this.name = "john"
    this.id = 12
    this.salary=5000
  }
}
const employee = new Employee()
employee.name = "Eric" 
console.log(employee.id)
button.id =11

Class Properties declaration

ES13 removed declaration of fields without this.

class Employee  {
  
  constructor() {
    name = "john"
    id = 12
    salary=5000
  }
}
const employee = new Employee()
employee.name = "Eric" 
console.log(employee.id)
button.id =11

Javascript Class instance member Fields

ES2022 was introduced to add public and private fields as seen below

We can define these properties as part of class level private files are declared starting with # and variable name

class Employee  {
      name = "john"
    id = 12
    #salary=5000
  constructor() {

  }
}

const employee = new Employee()
employee.name = "Eric" 
console.log(employee.id)
button.id =11

Static class fields and private static methods:

Static is a keyword that applies to fields and methods of a class in javascript.

These can be accessed without an instance of a class Static fields are applied to the class level.

Static can be applied.

  • properties
  • methods
  • blocks

if a variable is declared as static, called a static field in javascript. if there are multiple objects for the same class, there is only one value exists for all classes That means It is a common and global field value applicable to all instances of a class

Real-world use cases is a school name for all students and teachers.

class student{
  
  name;
  schoolName="Abc school"
}

if there are 1000 students, the schoolName property is repeated and allocated to memory.

To reduce the usage of memory, Static fields are introduced.

class student{
  
  name;
 static schoolName="Abc school"
}

In the above schoolName is public static property.

Let’s change this property to private.

declare a static variable by adding # symbol at the start

class student{
  
  name;
 static #schoolName="Abc school"
}

Let’s see static methods.

the static keyword is applied to the method

Here is a public static method

class student{
  
 let name;
 static #schoolName="Abc school"

  static getSchoolName() {
    return #schoolName
  }

Here is a private static method

class student{

let name;
static #schoolName="Abc school"

static #getSchoolName() {
  return #schoolName
}