Along with getter methods, we can also create setter methods which reassign values of existing properties within an object. Let’s see an example of a setter method:

const person = {
  _age: 37,
  set age(newAge){
    if (typeof newAge === 'number'){
      this._age = newAge;
    } else {
      console.log('You must assign a number to age');
    }
  }
};

Notice that in the example above:

• We can perform a check for what value is being assigned to this._age.
• When we use the setter method, only values that are numbers will reassign this._age
• There are different outputs depending on what values are used to reassign this._age.

Then to use the setter method:

person.age = 40;
console.log(person._age); // Logs: 40
person.age = '40'; // Logs: You must assign a number to age

Setter methods like age do not need to be called with a set of parentheses. Syntactically, it looks like we’re reassigning the value of a property.

Like getter methods, there are similar advantages to using setter methods that include checking input, performing actions on properties, and displaying a clear intention for how the object is supposed to be used. Nonetheless, even with a setter method, it is still possible to directly reassign properties. For example, in the example above, we can still set ._age directly:

person._age = 'forty-five'
console.log(person._age); // Prints forty-five