# Exercise: Coffee Shop Receipt

Finish six small functions that work out a coffee shop receipt's subtotal, tax, tip and lines, using numbers, strings, comparisons and conversions, and let the tests check each one.

Novice · JavaScript · Updated October 30, 2026

The Daily Grind's order app can take an order, but it can't print a receipt yet. Your job is to write the parts that work out the receipt: the subtotal, the sales tax, the tip, each line of the receipt, whether the customer's loyalty card has earned a free drink, and the quantity they typed. Each part is a small function for you to finish, and tests tell you when each one is right.

## 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 into your practice folder.

The folder holds:

- `receipt.js`: the six functions you'll finish.
- `print-receipt.js`: prints a whole receipt using your functions. Ready to use.
- `receipt.test.js`: the tests that check your functions. You don't need to change it.
- `package.json`: tells Node that the files share functions with `import` and `export`. Ready to use.

Open the folder in VS Code, and open a terminal there with **Terminal > New Terminal**.

## What to do

You'll write your own functions in the *Functions* chapter. Here, each function is already written except for its answer, so it works like a fill-in-the-blank. The names in parentheses are the values the function is handed, and whatever comes after `return` is its answer. Each one returns a placeholder for now. The comment above it says what it should return, with examples:

```javascript
/*
 * The price of one item times how many were ordered.
 *
 * subtotal(4.75, 2) -> 9.5
 * subtotal(3.25, 3) -> 9.75
 */
export function subtotal(price, quantity) {
  // TODO: replace 0 with your calculation.
  return 0;
}
```

`export` in front lets the tests and `print-receipt.js` use the function. Module 3's lesson *Modules: import and export* explains how that works; for now, leave it where it is.

1. **Name the tax rate.** The shop's sales tax is 8%. Give it a name with `const` at the top of `receipt.js`, where the comment says.
2. **Finish the money functions:** `subtotal`, then `salesTax` and `tip`, which round to the nearest cent.
3. **Finish `receiptLine`.** It returns one line of the receipt, such as `2 x Latte: $9.50`, built with a template literal.
4. **Finish `earnedFreeDrink` and `quantityFromText`:** a comparison, and a conversion from typed text to a number.

## Check your work

In the terminal, run the tests:

```bash
node --test
```

At first all six tests fail. That's expected: each function you finish turns its test green. When a test fails, its message says which values it used and what it expected, for example *The tax on $14.25 is 1.14. Without rounding it comes out as 1.1400000000000001.*

To see a whole receipt, run:

```bash
node print-receipt.js
```

## Hints

- **Work out an example by hand first.** What is 8% of $7.35? What is it to the nearest cent?
- **Rounding to cents takes three steps:** turn dollars into cents, round with `Math.round`, then turn cents back into dollars. *Numbers and Math* shows it.
- **A percent is a number out of 100.** 15% of an amount is the amount times 15, divided by 100.
- **A dollar sign before a blank** is written `$${...}` in a template literal; *Strings and Template Literals* explains why.
- **Typed text is always a string.** *Types and Converting Between Them* shows how to turn it into a number, and what you get for `'two'`.

## When you're done

All six tests pass, and `node print-receipt.js` prints:

```text
The Daily Grind
2 x Latte: $9.50
1 x Blueberry muffin: $3.25
Subtotal: $12.75
Sales tax: $1.02
Tip (20%): $2.55
Total: $16.32
Stamps on your card: 11. Free drink earned: true
```

Now look back at `salesTax`: if the tax rate went up to 9%, how many lines of your code would change? If the answer is more than one, look for a 0.08 that should be your `const`.

## So what

Every online checkout does what you built here: multiply, add tax and tip, round to the cent, and turn the numbers into readable text. Small functions, each checked by a test, are how real apps keep money right.

## Key terms

- [const](https://www.ask-codey.com/glossary/const-javascript)
- [Template Literal](https://www.ask-codey.com/glossary/template-literal)
- [Math Object](https://www.ask-codey.com/glossary/math-object)
- [Strict Equality (===)](https://www.ask-codey.com/glossary/strict-equality)
- [NaN](https://www.ask-codey.com/glossary/nan)

## Related

- [Variables with let and const](https://www.ask-codey.com/lessons/javascript-variables-let-and-const)
- [Numbers and Math](https://www.ask-codey.com/lessons/javascript-numbers-and-math)
- [Strings and Template Literals](https://www.ask-codey.com/lessons/javascript-strings-and-template-literals)
- [Booleans and Comparisons](https://www.ask-codey.com/lessons/javascript-booleans-and-comparisons)
- [Types and Converting Between Them](https://www.ask-codey.com/lessons/javascript-types-and-converting)

Source: https://www.ask-codey.com/lessons/exercise-javascript-coffee-shop-receipt