freeCodeCamp/guide/english/certifications/javascript-algorithms-and-data-structures/intermediate-algorithm-scripting/sum-all-numbers-in-a-range/index.md

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title: Sum All Numbers in a Range
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# Sum All Numbers in a Range

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## Problem Explanation

You need to create a program that will take an array of two numbers who are not necessarily in order, and then add not just those numbers but any numbers in between. For example, [3,1] will be the same as `1+2+3` and not just `3+1`


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## Hints

### Hint 1

Use `Math.max()` to find the maximum value of two numbers.

### Hint 2

Use `Math.min()` to find the minimum value of two numbers.

### Hint 3

Remember to that you must add all the numbers in between so this would require a way to get those numbers.


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## Solutions

<details><summary>Solution 1 (Click to Show/Hide)</summary>

```javascript
function sumAll(arr) {
  var max = Math.max(arr[0], arr[1]);
  var min = Math.min(arr[0], arr[1]);
  var temp = 0;
  for (var i = min; i <= max; i++) {
    temp += i;
  }
  return temp;
}

sumAll([1, 4]);
```


#### Code Explanation

*   First create a variable to store the max number between two.
*   The same as before for the Smallest number.
*   We create a temporary variable to add the numbers.

Since the numbers might not be always in order, using `max()` and `min()` will help organize.

#### Relevant Links

*   <a href='http://forum.freecodecamp.com/t/javascript-math-max/14682' target='_blank' rel='nofollow'>Math.max()</a>
*   <a href='http://forum.freecodecamp.com/t/javascript-math-min/14684' target='_blank' rel='nofollow'>Math.min()</a>
*   <a href='http://forum.freecodecamp.com/t/javascript-for-loop/14666' target='_blank' rel='nofollow'>For Loops</a>

</details>

<details><summary>Solution 2 (Click to Show/Hide)</summary>

```javascript
const sumAll = arr => {
  // Buckle up everything to one!
  const startNum = arr[0];
  const endNum = arr[1];

  // Get the count of numbers between the two numbers by subtracting them and add 1 to the absolute value.
  // ex. There are |1-4| + 1 = 4, (1, 2, 3, 4), 4 numbers between 1 and 4.
  const numCount = Math.abs(startNum - endNum) + 1;

  // Using Arithmetic Progression summing formula
  const sum = ((startNum + endNum) * numCount) / 2;
  return sum;
};
```

#### Code Explanation

*   The formula for calculating the sum of a continuous range is "(startNum + endNum) * numCount / 2".
*   arr[0] and arr[1] can either be startNum or endNum, order doesn't matter.
*   We can get the count of numbers in range by "Math.abs(arr[0] - arr[1]) + 1".
*   Applying the formula by plugging in the numbers.

#### Relevant Links

*   <a href='http://forum.freecodecamp.com/t/javascript-array-prototype-sort/14306' target='_blank' rel='nofollow'>Array.sort()</a>
*   <a href='https://en.wikipedia.org/wiki/Arithmetic_progression#Sum' target='_blank' rel='nofollow'>Arithmetic Progression summing formula</a>
*   <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions' target='_blank' rel='nofollow'>ES6 arrow function</a>
</details>


<details><summary>Solution 3 (Click to Show/Hide)</summary>

```javascript
function sumAll(arr) {
  var sum = 0;
  for (var i = Math.min(...arr); i <= Math.max(...arr); i++) {
    sum += i;
  }
  return sum;
}

sumAll([1, 4]);
```


#### Code Explanation

*   Creating a variable sum to store the sum of the elements.
*   Starting iteration of the loop from min element of given array and stopping when it reaches the max element.
*   Using a spread operator (...arr) allows passing the actual array to the function instead of one-by-one elements.

#### Relevant Links

*   <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_operator' target='_blank' rel='nofollow'>Spread Operator</a>
*   <a href='https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/max' target='_blank' rel='nofollow'>Using Spread Operator in Math.max()</a>
</details>