# Easing functions

Evaluate a common easing curve at progress t between 0 and 1.

Canonical: https://1loc.dev/misc/easing-functions/
Version: 1.0.0
Runtime: JavaScript · Node.js 22 / modern browsers
Verification: Local fixtures; no external services
Updated: 2026-10-28

## Implementation

```javascript
function ease({ name, t }) { return { linear: t, easeInQuad: t * t, easeOutQuad: t * (2 - t), easeInOutQuad: t < 0.5 ? 2 * t * t : -1 + (4 - 2 * t) * t, easeInCubic: t ** 3, easeOutCubic: (t - 1) ** 3 + 1 }[name]; }
```

## Input

```json
{
  "name": "easeInOutQuad",
  "t": 0.25
}
```

## Expected output

```json
0.125
```

## Edge case

Input:
```json
{
  "name": "easeOutQuad",
  "t": 1
}
```
Output:
```json
1
```

## Limits

- The original listed separate functions; one function selects the curve by name. Curves follow the gist the original cites (gre/1650294).
- Prefer CSS transitions for UI motion and honour prefers-reduced-motion.

The lab validates types and size before calling this function. Add equivalent validation at your own trust boundary.

## Source and license

Original: https://github.com/phuocng/1loc/blob/14b481cf60dff1620ab1bb99a43b1f68068cdd9b/contents/easing-functions.mdx
Author: Nguyen Huu Phuoc and original contributors
Contributors: See original repository history
Source commit: 14b481cf60dff1620ab1bb99a43b1f68068cdd9b
Copyright (c) 2020 phuoc-ng
License: MIT — https://1loc.dev/licenses/
Maintainer: Oveyon
Modifications: Combines the listed curves behind a name option. Original MDX retained as inert source evidence.