Methods with parameters and return values (JavaScript)

Name:

Date:

Class:

Quick Questions

Shade in the A or B circle for each question.

1. Which deposit method adds the amount AND gives the new balance back to the caller?

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

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

2. Which getArea() method correctly returns the area of a Rectangle object?

A getArea() { return this.width * this.height; }

B getArea() { return width * height; }

3. Which line calls deposit with 50 and saves the value it returns?

A const newBalance = account.deposit(50);

B const newBalance = deposit(50);

4. Which method returns a string such as 'Ava has 120 points' using a template literal?

A describe() { return ${this.name} has ${this.balance} points; }

B describe() { return '${this.name} has ${this.balance} points'; }

5. Where does the parameter amount in deposit(amount) get its value?

A It is a property that every object stores automatically

B From the argument passed in when the method is called, e.g. deposit(50)

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1deposit(amount) { this.balance += amount; return this.balance; }		Adescribe() { return `${this.name} has $${this.balance}`; }
2getArea() { return this.width * this.height; }		BThe properties are missing this. so the method looks for a variable called balance instead of the object's property. It should be this.balance.
3A method can take a parameter and use it with a property to work out a value to return.		CThe method never uses return, so the calculated area is thrown away and the caller gets undefined. It should be return this.width * this.height;
4A method can return a string built with a template literal using the object's properties.		DA method with no parameters that returns a number worked out from the object's width and height properties.
5deposit(amount) { balance += amount; return balance; }		EA method that takes an amount, adds it to the object's balance and returns the new balance.
6getArea() { this.width * this.height; }		FaddBonus(extra) { return this.points + extra; }

Definitions

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

Fill in the Blanks

Complete each line of code by filling in the missing parts.

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

deposit(amount) { this.balance __ amount; return this.balance; }

getArea() { return this.width _ this.height; }

getInfo() { return `${____.name} has ${this.points}`; }

const acc = new Account("Sam", 50); const newBal = acc._______(20); console.log(newBal);

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A class Account {

B deposit(amount) {

C balance += amount;

D return this.balance;

E }

F }

Question 2

A getArea {

B return this.side ** 2;

C }

Question 3

A greet() {

B return 'Hi ${this.name}!';

C }

Question 4

A const acc = new Account(50);

B const t = acc.deposit;

C console.log(t);

Question 5

A class Wallet {

B spend(amount) {

C this.cash -= amount;

D return amount;

E }

F }

Answer Key

Methods with parameters and return values (JavaScript)

Section A: Quick Questions

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

A — getArea() { return this.width * this.height; }

A — const newBalance = account.deposit(50);

A — describe() { return ${this.name} has ${this.balance} points; }

B — From the argument passed in when the method is called, e.g. deposit(50)

Section B: Match the Pairs

deposit(amount) { this.balance += amount; return this.balance; } → A method that takes an amount, adds it to the object's balance and returns the new balance.

getArea() { return this.width * this.height; } → A method with no parameters that returns a number worked out from the object's width and height properties.

A method can take a parameter and use it with a property to work out a value to return. → addBonus(extra) { return this.points + extra; }

A method can return a string built with a template literal using the object's properties. → describe() { return `${this.name} has $${this.balance}`; }

deposit(amount) { balance += amount; return balance; } → The properties are missing this. so the method looks for a variable called balance instead of the object's property. It should be this.balance.

getArea() { this.width * this.height; } → The method never uses return, so the calculated area is thrown away and the caller gets undefined. It should be return this.width * this.height;

Section C: Definitions

deposit(amount) { this.balance += amount; return this.balance; } — A class method takes a parameter (amount) and uses return to give back a value worked out from the object's properties, such as the new balance.

Section D: Fill in the Blanks

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

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

getArea() {
  return this.width * this.height;
}

getInfo() {
  return `${this.name} has ${this.points}`;
}

const acc = new Account("Sam", 50);
const newBal = acc.deposit(20);
console.log(newBal);

Section E: Spot the Error

C — Inside a method, the object's property must be reached with this. Without this, balance is treated as a separate variable and causes a ReferenceError. It should be this.balance += amount;

A — A method needs parentheses after its name, even when it takes no parameters. It should be getArea() {

B — Template literals must use backticks. With single quotes, ${this.name} is not replaced and the text is returned as-is. It should be return `Hi ${this.name}!`;

B — Without parentheses the method is never called, so t holds the function instead of the returned balance. It should be const t = acc.deposit(20);

D — This returns the parameter that was passed in, not the new value worked out from the object's property. It should be return this.cash;