JavaScript Object Getter and Setter Methods

Getter

Getter methods are used to return an object's properties.

See the examples below:

const person = {
  name: 'Bello',
  age: 27,
  getPerson() {
    if (typeof this.name === 'string' && typeof this.age === 'number') {
      return `${this.name} is ${this.age} years old!`;
    }

    return "Name or age is invalid";
  } 
}

console.log( person.getPerson() );

We can add a little more get keyboard to the code snippet above.

const person = {
  name: 'Bello',
  age: 27,
  get getPerson() {
    if (typeof this.name === 'string' && typeof this.age === 'number') {
      return `${this.name} is ${this.age} years old!`;
    }

    return "Name or age is invalid";
  } 
}

console.log(person.getPerson); //  No parenthesis used

The difference is when the get keyword was used, no parenthesis was used in the calling function.

getPerson, not getPerson()."

The name property

A function in on object looks like a property when the get keyword is used.

See the example:

const sayHi = {
  get name() {
    return "Hello World!";
  }
};

sayHi.name; // "Hello World!"

The syntax above looks like object.property syntax.

We can get the name of a function with the name property.

See the example below:

function greet() {
  return "Hello World!";
}

console.log(greet.name); // greet

A function name can also be accessible even if used as a default parameter in another function.

function func(greet = function() {}) {
  console.log(greet.name); // greet
}

func();

The length property

The length or the number of parameters of a function can also be accessible by the length property.

See the example below:

const func = (name, age) => {
  return "${name} is ${age} today!";
}

console.log(func.length); // 2

Setter

Setter methods are used to set or reassign values of existing properties within an object.

const person = {
  name: 'Bello',
  age: 27
} 

person.name = 'John';
console.log(person.name) // John;

We can do more than the example above by checking if certain properties exist in an object. In the example below, an existing property gets reassigned

const person = {
  name: 'Bello',

  set setPerson(name) {
    if (this.name) {
      this.name = name;
    } else { 
      console.log("Give a valid name");
    }
  } 

};

person.setPerson = 'John';
console.log(person.name, typeof person.name) // John string