[Intermediate Algorithm Scripting: Sum All Numbers in a Range | freeCodeCamp.org](https://www.freecodecamp.org/learn/javascript-algorithms-and-data-structures/intermediate-algorithm-scripting/sum-all-numbers-in-a-range)

```js function sumAll(arr) {}

sumAll([1, 4]) ```

我做出来了！

```js function sumAll(arr) { const newArr = arr.sort((a, b) => a - b) return ((newArr[1] + newArr[0]) * (newArr[1] - newArr[0] + 1)) / 2 }

sumAll([5, 10]) ```

思路：

我在想如果是我要计算，应该怎么做？我会这样：

(上底 + 下底) x 高/2