# Exercise: Fun Run Sign-Ups

Finish seven functions that tidy a 5K fun run's messy sign-ups, from names and bib numbers to missing shirt sizes, donations and emergency contacts, and save and load the list as JSON, with tests that check each one.

Apprentice · JavaScript · Updated October 30, 2026

The Riverside 5K Fun Run is on Saturday, and the volunteers at the check-in table need a clean list. The sign-up form saved names like `  mARIA  lopez ` and `jamal REED`, some runners skipped the shirt size, one left the donation box blank while another typed 0 on purpose, and two have no emergency contact. You'll finish seven small functions that tidy it all up, and tests tell you when each one works. When you're done, one command prints the whole check-in sheet.

## 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 `javascript-course` folder.

The folder holds:

- `signups.js`: the seven functions. For you to finish.
- `report.js`: prints the check-in sheet using your functions, and saves the tidied list as `checked-in.json`. Ready to use.
- `signups.json`: the four runners' sign-ups, as the form saved them, messy text and all. Ready to use.
- `signups.test.js`: the tests that check your functions. You don't need to change this file.
- `package.json`: tells Node.js how to run this folder's code and its tests. Ready to use.

In VS Code, choose **File > Open Folder** and open the exercise's folder. You only need Node.js: there's nothing to install with npm.

## What to do

Every function in `signups.js` is already declared and returns a placeholder (`''`, `0` or `[]`) for now. The comment above each one says what it should return, with examples:

```javascript
/*
 * The number printed on a runner's bib: always at least four digits, with zeros in front.
 * A number that already has four or more digits stays as it is.
 *
 * bibNumber(7) -> '0007'
 * bibNumber(58) -> '0058'
 * bibNumber(12345) -> '12345'
 */
export function bibNumber(number) {
  // TODO: replace '' with your code.
  return '';
}
```

1. **Tidy the text.** Finish `tidyName` (`'  mARIA  lopez '` becomes `'Maria Lopez'`) and `bibNumber` (`7` becomes `'0007'`).
2. **Fill the gaps.** Finish `shirtSize` (an M for anyone who didn't pick), `donation` (the suggested $10 for a blank box, while a 0 stays 0) and `emergencyPhone` (the contact's phone, or *No emergency contact*, without ever stopping the program).
3. **Save and load.** Finish `saveSignups`, which turns the list into JSON text indented by 2 spaces, and `loadSignups`, which reads it back and returns `[]` when the text is broken.

## Check your work

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

```bash
node --test
```

At first all 8 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 *Jamal's emergencyContact is null. Reading .phone of null stops the program: ?. reads it safely.*

To see the check-in sheet, run:

```bash
node report.js
```

## Hints

- **Work `tidyName` out by hand first.** What does `split(' ')` give you for `'  mARIA  lopez '`? *String Methods* shows what to do with the empty pieces, and how to fix one word with `slice`.
- **Do the same thing to every word.** `map`, from *map and filter*, fixes each word, and `join` puts them back together.
- **Numbers don't have string methods.** `padStart` works on a string, and a bib number arrives as a number.
- **0 is a real donation.** *Missing Values: null, undefined, ?. and ??* shows which default operator keeps it.
- **Broken JSON throws an error.** *JSON: Data You Can Save and Send* shows how `try` and `catch` let the program carry on.

## When you're done

All 8 tests are green, and `node report.js` prints:

```text
Riverside 5K check-in sheet: 4 runners
0007  Maria Lopez   shirt M   $25   555-555-0142
0012  Jamal Reed    shirt XL  $10   No emergency contact
0058  Priya Shah    shirt S   $0    555-555-0177
0103  Sam Okafor    shirt M   $10   No emergency contact
Saved checked-in.json: 733 characters.
```

Open `checked-in.json` and look at Priya: is her donation still 0? Then change the `??` in `donation` to `||`, run the tests again, and read which test turns red, and why.

## So what

Every app that takes sign-ups, orders or reviews has a function like these behind it, cleaning what people type before anyone else sees it. Tidy text, sensible defaults and JSON that survives a bad file are what make that data trustworthy.

## Key terms

- [split()](https://www.ask-codey.com/glossary/split-javascript)
- padStart()
- [Optional Chaining](https://www.ask-codey.com/glossary/optional-chaining)
- [Nullish Coalescing](https://www.ask-codey.com/glossary/nullish-coalescing)
- [JSON.stringify()](https://www.ask-codey.com/glossary/json-stringify)
- [JSON.parse()](https://www.ask-codey.com/glossary/json-parse)

## Related

- [String Methods](https://www.ask-codey.com/lessons/javascript-text-string-methods)
- [Equality and Truthy Values](https://www.ask-codey.com/lessons/javascript-tricky-values-equality-and-truthiness)
- [Missing Values: null, undefined, ?. and ??](https://www.ask-codey.com/lessons/javascript-tricky-values-null-and-undefined)
- [JSON: Data You Can Save and Send](https://www.ask-codey.com/lessons/javascript-json-stringify-and-parse)

Source: https://www.ask-codey.com/lessons/exercise-javascript-fun-run-sign-ups