Getters and Setters for objects in JavaScript

Published July 30, 2020

Getters and setters in objects feel like real properties but it's not real properties but a computed property.

First, Let me tell what a getter in the object is.

Consider this object John,

// John Object
const John = {
  firstName: "John",
  lastname: "Doe",
  baseSalary: 23000,
  allowance: 3000,
};

So this is a good old object with properties firstName, lastname, baseSalary, and allowance.

What if we need another property called grossSalary which is the total of baseSalary and allowance in the object John, but without defining an actual property on the John object.

So that we can get the value of grossSalary by calling John.grossSalary.

Here, we can use the concept of a getter in an object.

To make a getter in the object you need to use the get keyword followed by the property name that we can call in the object.

let's make a getter called grossSalary.

// John Object
const John = {
  firstName: "John",
  lastname: "Doe",
  baseSalary: 23000,
  allowance: 3000,
  // getter grossSalary
  // this returns baseSalary + allowance
  get grossSalary() {
    return this.baseSalary + this.allowance;
  },
};

Now if you try to call John.grossSalary it returns the value by adding the baseSalary property and allowance property.

// John Object
const John = {
  firstName: "John",
  lastname: "Doe",
  baseSalary: 23000,
  allowance: 3000,
  // getter grossSalary
  // this returns baseSalary + allowance
  get grossSalary() {
    return this.baseSalary + this.allowance;
  },
};

// get grossSalary
// just like calling a regular property
console.log(John.grossSalary);

This is why it is also called as computed properties. Because the grossSalary is not a property but a computed property of baseSalary property and allowance property.

Yeah! 🚀 We made a Getter.

Now, let's understand what a setter in an object is.

Just from the word itself, it means it's used to set a property value.

To make a setter in an object you need to use the set keyword followed by the property name that we can call in the object.

Let's define a setter called fullName.

// John Object
const John = {
  firstName: "John",
  lastname: "Doe",
  baseSalary: 23000,
  allowance: 3000,
  // getter grossSalary
  // this returns baseSalary + allowance
  get grossSalary() {
    return this.baseSalary + this.allowance;
  },

  // setter fullName
  // this sets the value for both the firstName and lastName property
  set fullName(fullName) {
    // we are splitting the fullname by space
    // split method returns an array
    const namesArr = fullName.split(" ");
    this.firstName = namesArr[0];
    this.lastName = namesArr[1];
  },
};

We have defined a setter called fullName which sets the value for firstName and lastName properties by splitting up the full name value by a space " ".

So lets set a value for fullName property.

// John Object
const John = {
  firstName: "John",
  lastname: "Doe",
  baseSalary: 23000,
  allowance: 3000,
  // getter grossSalary
  // this returns baseSalary + allowance
  get grossSalary() {
    return this.baseSalary + this.allowance;
  },

  // setter fullName
  // this sets the value for both the firstName and lastName property
  set fullName(fullName) {
    // we are splitting the fullname by space
    // split method returns an array
    const namesArr = fullName.split(" ");
    this.firstName = namesArr[0];
    this.lastName = namesArr[1];
  },
};

// lets set value for fullName
// which actually sets value for firstName and lastName property
John.fullName = "Lily Rose";

// see the contents of John object
console.log(John);

Now if you look into the contents of John object you can see that the firstName and lastName properties values are changed.

A bit of quick advice to you is that if you are making a setter it's better to make a getter for it.

Let's make a getter for fullName property.

// John Object
const John = {
  firstName: "John",
  lastname: "Doe",
  baseSalary: 23000,
  allowance: 3000,
  // getter grossSalary
  // this returns baseSalary + allowance
  get grossSalary() {
    return this.baseSalary + this.allowance;
  },

  // setter fullName
  // this sets the value for both the firstName and lastName property
  set fullName(fullName) {
    // we are splitting the fullname by space
    // split method returns an array
    const namesArr = fullName.split(" ");
    this.firstName = namesArr[0];
    this.lastName = namesArr[1];
  },

  // getter fullName
  get fullName() {
    return `${this.firstName} ${this.lastName}`;
  },
};

// lets set value for fullName
// which actually sets value for firstName and lastName property
John.fullName = "Lily Rose";

console.log(John.fullName);

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