How to Access TypeScript Private Members ?

In this TypeScript article, we will learn how to access the TypeScript private members using different approaches. We can interact with the encapsulated components within the class and access them in the application.

There are three different approaches through which we can access TypeScript private members.

Using any Type

In this approach, we are using any Type to access private members. In the example, we have privateVar in the GFGClass which is accessed using any type assertion by bypassing the TypeScript’s encapsulation.

Syntax:

let variableName: any = 'This can be any type';

Example: Below is the implementation of the above-discussed approach.

Javascript

class GFGClass {
    private privateVar: string = 
    'Hey Geek! This is Private Data';
    public accessFn() {
        return (obj as any).privateVar;
    }
}
const obj = new GFGClass();
console.log(obj.accessFn()); 

Output:

"Hey Geek! This is Private Data" 

Using Reflect

In this approach, we are using Reflect to access private members. We have a private member as data2 in the GFGClass2 which is accessed using Reflect.get(this, ‘data2’). This approach reflects on the object instance to retrieve the value of the private member.

Syntax:

Reflect.get(target: any, propertyKey: PropertyKey, receiver?: any): any;

Example: Below is the implementation of the above-discussed approach.

Javascript

class GFGClass2 {
  private data2: 
  string = 'Private Variable accessed using Reflect';
  public accessFn() {
    const privateVar = 
    Reflect.get(this, 'data2');
    console.log(privateVar);
  }
}
const myObject = new GFGClass2();
myObject.accessFn(); 

Output:

"Private Variable accessed using Reflect"

Using square bracket([]) Notation

In this approach, we are using square bracket([]) Notation to access the private members of the Class. We have defined the private variable as data3 and the private function as privateFn in GFGClass3. We are accessing this member using [] notation and type assertion to any.

Syntax:

const value = (object as any)['propertyName'];

Example: Below is the implementation of the above-discussed approach.

Javascript

class GFGClass3 {
  private data3: string = 
  'This is Private Variable';
  private privateFn(): void {
    console.log(
    'This is Private Function Called');
  }
  public accessFn3() {
    const privateVar = 
    (this as any)['data3'];
    console.log(privateVar);
    const privateFunction = 
    (this as any)['privateFn'];
    privateFunction.call(this);
  }
}
const myObject = new GFGClass3();
myObject.accessFn3();

Output:

"This is Private Variable" 
"This is Private Function Called"

Using ES6 WeakMap

In this approach, we utilize ES6 WeakMap to access private members. WeakMap allows us to store key-value pairs where the keys are objects and the values can be arbitrary data. We can use WeakMap to store private members and access them indirectly using class methods.

Syntax:

const privateData = new WeakMap();

Example: Below is the implementation of the above-discussed approach.

JavaScript

const privateData = new WeakMap();

class GFGClass4 {
  constructor() {
    privateData.set(this, { privateVar: 'Private Data using WeakMap' });
  }

  public accessFn4() {
    const privateVar = privateData.get(this)?.privateVar;
    console.log(privateVar);
  }
}

const myObject = new GFGClass4();
myObject.accessFn4();

Output:

Private Data using WeakMap