# Exercise: Bike Rental Prices

Finish four functions for a bike rental shop, using conditions, the conditional operator and a for loop, and let the tests check every price, bike size and group receipt.

Apprentice · JavaScript · Updated October 30, 2026

Hilltop Bikes works out every price by hand, on a notepad at the counter: is it the weekend, is the rider a member, did the rental hit the day cap? On a busy Saturday, with a family of five waiting, mistakes happen. In this exercise you write the code that does it for them: four small functions, with tests that check every one as you go.

## Get the exercise code

In the **Exercise** box beside the lesson, choose **Get the starter on GitHub** to open its GitHub repository. Click **Code**, then **Download ZIP**, and unzip it wherever you keep your practice work. Then open the folder in VS Code.

The folder holds:

- `rentals.js`: the four functions for you to finish.
- `app.js`: prints your functions' answers for a few customers, so you can see them at work.
- `rentals.test.js`: the tests that check your functions. You don't need to change these.
- `package.json`: tells Node that these files use `import` and `export`.

## What to do

Each function in `rentals.js` is already written except for its body. The values in its parentheses are its inputs: variables that already hold a value when the function runs. `return` hands back the answer and ends the function on that line. The next chapter, *Functions*, shows how to write functions of your own; here you only fill them in.

The comment above each function says what it should give back, with examples:

```javascript
/*
 * Give back true when the day is "Saturday" or "Sunday", and false for every other day.
 * Days always start with a capital letter.
 *
 * isWeekend("Saturday") -> true
 * isWeekend("Sunday")   -> true
 * isWeekend("Monday")   -> false
 */
export function isWeekend(day) {
  return false;
}
```

The shop's prices are at the top of the file: $12 an hour on weekdays and $15 on weekends, members pay $2 less an hour, and a rental never costs more than the day cap of $60 on a weekday or $75 on a weekend.

1. **Finish `isWeekend`.** It gives back `true` for Saturday or Sunday.
2. **Finish `rentalPrice(hours, isWeekendDay, isMember)`.** Pick the hourly rate, take off the member discount, multiply, and apply the day cap.
3. **Finish `bikeSize(height)`.** Under 54 inches is `"kids"`, under 63 `"small"`, under 69 `"medium"`, and taller is `"large"`.
4. **Finish `groupReceipt(riders, hours, isWeekendDay)`.** One line per bike, then the total. Every fourth bike is free, and a one-hour ride says `1 hour`, not `1 hours`.

## Check your work

In VS Code, open a terminal in the folder (**Terminal > New Terminal**) and run the tests:

```bash
node --test
```

At first every test fails. That's expected: each function you finish turns its tests green. When a test fails, its message says which values it used and what it expected, for example *6 hours on a weekday is 72 by the hour, so it should cost the cap: 60.*

To see your functions' answers, run `node app.js`.

## Hints

- **Work out an example by hand first.** For 7 hours on a weekday, for a member: what's the hourly rate, the price before the cap, and the cap?
- **One condition, two values.** The weekend decides both the hourly rate and the day cap. The conditional operator from *switch and the Conditional Operator* picks a value in one line.
- **Order matters.** In `bikeSize`, check the smallest size first, as in *Making Decisions with if and else*.
- **Use what you've built.** `groupReceipt` needs each bike's price, and `rentalPrice` already works it out.
- **Which bikes are free?** `%` gives the remainder of a division. Bike 4 and bike 8 have a remainder of 0 when you divide them by 4. `continue`, from *Counting with for*, can skip the rest of a pass.

## When you're done

Every test is green, and `node app.js` prints:

```text
Is Saturday a weekend day? true
Is Tuesday a weekend day? false
3 hours on a weekday: $36
3 hours on a weekend, for a member: $39
8 hours on a weekend: $75
A rider 66 inches tall rides a medium bike.

A group of 5, riding 2 hours on a weekday:
Bike 1: 2 hours, $24
Bike 2: 2 hours, $24
Bike 3: 2 hours, $24
Bike 4: 2 hours, free
Bike 5: 2 hours, $24
Total: $96
```

Now say Hilltop Bikes raises its weekend rate to $16. How many lines of your code do you need to change? If the answer is more than one, look for a 15 that appears in two places.

## So what

Every price on a checkout page, from bike rentals to plane tickets, is a handful of rules like these: conditions for the special cases, and a loop for each item. You've written the real thing.

## Key terms

- [if Statement](https://www.ask-codey.com/glossary/if-statement-javascript)
- [Logical Operators](https://www.ask-codey.com/glossary/logical-operators-javascript)
- [Ternary Operator](https://www.ask-codey.com/glossary/ternary-operator-javascript-2)
- [for Loop](https://www.ask-codey.com/glossary/for-loop-javascript)
- [continue](https://www.ask-codey.com/glossary/continue-javascript)

## Related

- [Making Decisions with if and else](https://www.ask-codey.com/lessons/javascript-conditions-if-and-else)
- [Combining Conditions with And, Or and Not](https://www.ask-codey.com/lessons/javascript-conditions-and-or-not)
- [switch and the Conditional Operator](https://www.ask-codey.com/lessons/javascript-conditions-switch-and-ternary)
- [Counting with for](https://www.ask-codey.com/lessons/javascript-loops-for)

Source: https://www.ask-codey.com/lessons/exercise-javascript-bike-rental-prices