---
id: 5ddb965c65d27e1512d44dad
title: Part 20
challengeType: 0
isHidden: true
---
## Description
<section id='description'>
Let's says we have an array `[1, 3, 5]` named `arr` and we want to sum up all the numbers.
We can use the reduce function as follows:
```js
arr.reduce((accumulator, currentValue) => {
return accumulator + currentValue;
}, 0);
```
At `arr[0]`, the function is `(0, 1) => { return 0 + 1 }`,
since `arr[0] = 1 = currentValue`.
At `arr[1]`, the function is `(1, 3) => 1 + 3`,
Finally at `arr[2]`, the function is `(4, 5) => 4 + 5`. Now the accumulator is `9` and since we have gone through all of the items in `arr`, the `reduce()` method will return `9`.
In the body of the callback function, replace `/* code to run */` with `return accumulator + currentValue`.
</section>
## Instructions
<section id='instructions'>
</section>
## Tests
<section id='tests'>
```yml
tests:
- text: See description above for instructions.
testString: assert( code.replace(/\s/g, '').match(/reduce\(\(accumulator\,currentValue\)\=\>{returnaccumulator\+currentValue\;?},0\)/) );
```
</section>
## Challenge Seed
<section id='challengeSeed'>
<div id='html-seed'>
```html
<script>
document.getElementById('calorie-form').onsubmit = calculate;
function calculate(e) {
e.preventDefault();
const total = Array.from(document.getElementsByClassName('cal-control'))
.map(meal => Number(meal.value))
.reduce((accumulator, currentValue) => {
/* code to run */
}, 0);
}
</script>
```
</div>
### Before Test
<div id='html-setup'>
```html
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title></title>
<meta name="description" content="" />
<meta name="viewport" content="width=device-width, initial-scale=1" />
<link rel="stylesheet" href="styles.css" />
</head>
<body>
<div class="container">
<form id="calorie-form">
<h2 class="center">Calorie Counter</h2>
<div class="grid">
<legend>Sex</legend>
<div>
<input type="radio" name="sex" id="female" value="F" checked />
<label for="female">
Female (2,000 calories)
</label>
<div>
<input type="radio" name="sex" id="male" value="M" />
<label for="male">
Male (2,500 calories)
</label>
</div>
</div>
</div>
<div class="grid" id="entries">
Breakfast
<input
type="number"
min="0"
class="cal-control"
id="breakfast"
/><br />
Lunch
<input type="number" min="0" class="cal-control" id="lunch" /><br />
Dinner <input type="number" min="0" class="cal-control" id="dinner" />
</div>
<button type="button" class="btn-add" id="add">
Add Entry
</button>
<button type="submit" class="btn-solid" id="calculate">
Calculate
</button>
<button type="button" class="btn-outline" id="clear">
Clear
</button>
</form>
<div id="output"></div>
</div>
</body>
</html>
```
</div>
### After Test
<div id='html-teardown'>
```html
</body>
</html>
```
</div>
</section>
## Solution
<section id='solution'>
```html
<script>
document.getElementById('calorie-form').onsubmit = calculate;
function calculate(e) {
e.preventDefault();
const total = Array.from(document.getElementsByClassName('cal-control'))
.map(meal => Number(meal.value))
.reduce((accumulator, currentValue) => {
return accumulator + currentValue;
}, 0);
}
</script>
```
</section>