---
id: 635089e3bd3e144f2db4094f
title: Step 18
challengeType: 0
dashedName: step-18
---

# --description--

Se provi il modulo con un elenco di numeri, dovresti vedere la media sulla pagina. Tuttavia, questo funziona solo perché l'iframe di freeCodeCamp ha delle impostazioni speciali. Normalmente, quando un modulo viene inviato, l'evento attiva un aggiornamento della pagina.

Per risolvere questo problema, aggiungi `return false;` dopo la chiamata `calculate();` nell'attributo `onsubmit`.

# --hints--

L'attributo `onsubmit` dovrebbe avere un'istruzione `return false;`.

```js
assert.match(document.querySelector("form").getAttribute("onsubmit"), /return\s+false;/);
```

L'attributo `onsubmit` dovrebbe ancora chiamare `calculate()`.

```js
assert.match(document.querySelector("form").getAttribute("onsubmit"), /calculate\(\s*\)/);
```

Dovresti restituire `false` dopo aver chiamato `calculate()`.

```js
assert.match(document.querySelector("form").getAttribute("onsubmit"), /calculate\(\s*\);\s*return\s+false;/);
```

# --seed--

## --seed-contents--

```html
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <link rel="stylesheet" href="./styles.css" />
    <script src="./script.js"></script>
    <title>Statistics Calculator</title>
  </head>
  <body>
    <h1>Statistics Calculator</h1>
    <p>Enter a list of comma-separated numbers.</p>
--fcc-editable-region--
    <form onsubmit="calculate();">
--fcc-editable-region--
      <label for="numbers">Numbers:</label>
      <input type="text" name="numbers" id="numbers" />
      <button type="submit">Calculate</button>
    </form>
    <div class="results">
      <p>
        The <dfn>mean</dfn> of a list of numbers is the average, calculated by
        taking the sum of all numbers and dividing that by the count of numbers.
      </p>
      <p class="bold">Mean: <span id="mean"></span></p>
      <p>
        The <dfn>median</dfn> of a list of numbers is the number that appears in
        the middle of the list, when sorted from least to greatest.
      </p>
      <p class="bold">Median: <span id="median"></span></p>
      <p>
        The <dfn>mode</dfn> of a list of numbers is the number that appears most
        often in the list.
      </p>
      <p class="bold">Mode: <span id="mode"></span></p>
      <p>
        The <dfn>range</dfn> of a list of numbers is the difference between the
        largest and smallest numbers in the list.
      </p>
      <p class="bold">Range: <span id="range"></span></p>
      <p>
        The <dfn>variance</dfn> of a list of numbers measures how far the values
        are from the mean, on average.
      </p>
      <p class="bold">Variance: <span id="variance"></span></p>
      <p>
        The <dfn>standard deviation</dfn> of a list of numbers is the square
        root of the variance.
      </p>
      <p class="bold">
        Standard Deviation: <span id="standardDeviation"></span>
      </p>
    </div>
  </body>
</html>
```

```css
body {
  margin: 0;
  background-color: rgb(27, 27, 50);
  text-align: center;
  color: #fff;
}

button {
  cursor: pointer;
  background-color: rgb(59, 59, 79);
  border: 3px solid white;
  color: white;
}

input {
  background-color: rgb(10, 10, 35);
  color: white;
  border: 1px solid rgb(59, 59, 79);
}

.bold {
  font-weight: bold;
}
```

```js
const getMean = (array) => array.reduce((acc, el) => acc + el, 0) / array.length;

const calculate = () => {
  const value = document.querySelector("#numbers").value;
  const array = value.split(/,\s*/g);
  const numbers = array.map(el => Number(el)).filter(el => !isNaN(el));

  const mean = getMean(numbers);

  document.querySelector("#mean").textContent = mean;
}
```
