Summary - Objects

Build a bank account app using objects and methods.

Summary - Bank account

In this lesson we combine objects, properties, methods and this to build a simple bank account app. The account object holds a balance and lets you add or withdraw money with deposit and withdraw methods.

const account = {
  owner: 'Alex',
  balance: 0
};

First we'll create the account and add a deposit method, then add a withdraw method. At each step we'll update the same object's balance with this.balance.

Exercise Create a bank account

Create an object named account. It should have owner set to 'Alex' and balance set to 0. With the shorthand, define a deposit method: it takes an amount parameter, adds it to this.balance and returns the new balance. Then call console.log(account.deposit(100)).

Show example solution

const account = {
  owner: 'Alex',
  balance: 0,
  deposit(amount) {
    this.balance = this.balance + amount;
    return this.balance;
  }
};
console.log(account.deposit(100));

Exercise Add a withdraw method

Add a withdraw method to the account object below. It takes an amount parameter, subtracts it from this.balance and returns the new balance. Then call console.log(account.withdraw(30)).

Show example solution

const account = {
  owner: 'Alex',
  balance: 100,
  deposit(amount) {
    this.balance = this.balance + amount;
    return this.balance;
  },
  withdraw(amount) {
    this.balance = this.balance - amount;
    return this.balance;
  }
};
console.log(account.withdraw(30));

Test yourself

How does deposit update this.balance?
```
deposit(amount) {
  this.balance = ?;
}
```
- balance + amount
- this + amount
- this.balance + amount
- amount
Show answer

this.balance + amount — Correct! this.balance + amount gives the new balance.

Complete the deposit method

deposit(amount) {
  this.balance = this.balance ____ amount;
  return this.balance;
}

Show answer

deposit(amount) {
  this.balance = this.balance + amount;
  return this.balance;
}

Match the concepts

{ }

object literal
user.name

dot notation
this.balance

access in a method

Next lesson: Project: Quiz app

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