---
id: 5d79253a98bd9fdf7ce68d0a
title: Part 137
challengeType: 0
dashedName: part-137
---
# --description--
We've used recursion in `range`, but recursion can have performance issues in JavaScript. If performance is an issue, you should try to use a higher order function like `reduce`, and if you can't do that, you'll probably have to use a for/while loop.
While we don't expect the user to enter particularly large numbers so that performance is an issue, we're going to refactor `range` as an exercise.
Replace the body of `range` with `start`.
# --hints--
See description above for instructions.
```js
assert(
/constrange=\(start,end\)=>start(;|const)/.test(code.replace(/\s/g, ''))
);
```
# --seed--
## --before-user-code--
```html
Spreadsheet
```
## --after-user-code--
```html
```
## --seed-contents--
```html
```
# --solutions--
```html
```