Using Getters and Setters in JavaScript

Getters and setters let you intercept property reads and writes on an object. The caller uses normal dot notation, but under the hood you control what happens.

Creating a Getter in TypeScript

Use the get keyword before a method name:

class MyClass {
  private _myProperty: string = 'default value';

  get myProperty(): string {
    return this._myProperty;
  }
}

const myObject = new MyClass();

console.log(myObject.myProperty); // Output: 'default value'

Creating a Setter in TypeScript

Add a setter with the set keyword to handle writes:

class MyClass {
  private _myProperty: string = 'default value';

  get myProperty(): string {
    return this._myProperty;
  }

  set myProperty(value: string) {
    this._myProperty = value;
  }
}

const myObject = new MyClass();

myObject.myProperty = 'new value';
console.log(myObject.myProperty); // Output: 'new value'

Common use cases for Getters and Setters

A setter can validate or clamp a value before storing it:

class MyClass {
  private _myProperty: number = 0;

  get myProperty(): number {
    return this._myProperty;
  }

  set myProperty(value: number) {
    if (value < 0) {
      this._myProperty = 0;
    } else if (value > 100) {
      this._myProperty = 100;
    } else {
      this._myProperty = value;
    }
  }
}

const myObject = new MyClass();

myObject.myProperty = -10;
console.log(myObject.myProperty); // Output: 0

myObject.myProperty = 200;
console.log(myObject.myProperty); // Output: 100

myObject.myProperty = 50;
console.log(myObject.myProperty); // Output: 50

Getters also work well for derived values:

class MyClass {
  private _myArray: number[] = [];

  get myArrayLength(): number {
    return this._myArray.length;
  }

  addValueToMyArray(value: number) {
    this._myArray.push(value);
  }
}

const myObject = new MyClass();

myObject.addValueToMyArray(1);
myObject.addValueToMyArray(2);
myObject.addValueToMyArray(3);

console.log(myObject.myArrayLength); // Output: 3

Conclusion

Getters and setters are most valuable when the implementation needs to change without breaking the public API — validation, computed properties, and lazy initialization all fit naturally here.