---
id: easing
title: Easing
layout: docs
category: APIs
permalink: docs/easing.html
next: geolocation
previous: dimensions
---

The `Easing` module implements common easing functions. This module is used
by [Animate.timing()](docs/animate.html#timing) to convey physically
believable motion in animations.

You can find a visualization of some common easing functions at
http://easings.net/

### Predefined animations

The `Easing` module provides several predefined animations through the
following methods:

- [`back`](docs/easing.html#back) provides a simple animation where the
  object goes slightly back before moving forward
- [`bounce`](docs/easing.html#bounce) provides a bouncing animation
- [`ease`](docs/easing.html#ease) provides a simple inertial animation
- [`elastic`](docs/easing.html#elastic) provides a simple spring interaction

### Standard functions

Three standard easing functions are provided:

- [`linear`](docs/easing.html#linear)
- [`quad`](docs/easing.html#quad)
- [`cubic`](docs/easing.html#cubic)

The [`poly`](docs/easing.html#poly) function can be used to implement
quartic, quintic, and other higher power functions.

### Additional functions

Additional mathematical functions are provided by the following methods:

- [`bezier`](docs/easing.html#bezier) provides a cubic bezier curve
- [`circle`](docs/easing.html#circle) provides a circular function
- [`sin`](docs/easing.html#sin) provides a sinusoidal function
- [`exp`](docs/easing.html#exp) provides an exponential function

The following helpers are used to modify other easing functions.

- [`in`](docs/easing.html#in) runs an easing function forwards
- [`inOut`](docs/easing.html#inout) makes any easing function symmetrical
- [`out`](docs/easing.html#out) runs an easing function backwards


### Methods

- [`step0`](docs/easing.html#step0)
- [`step1`](docs/easing.html#step1)
- [`linear`](docs/easing.html#linear)
- [`ease`](docs/easing.html#ease)
- [`quad`](docs/easing.html#quad)
- [`cubic`](docs/easing.html#cubic)
- [`poly`](docs/easing.html#poly)
- [`sin`](docs/easing.html#sin)
- [`circle`](docs/easing.html#circle)
- [`exp`](docs/easing.html#exp)
- [`elastic`](docs/easing.html#elastic)
- [`back`](docs/easing.html#back)
- [`bounce`](docs/easing.html#bounce)
- [`bezier`](docs/easing.html#bezier)
- [`in`](docs/easing.html#in)
- [`out`](docs/easing.html#out)
- [`inOut`](docs/easing.html#inout)




---

# Reference

## Methods

### `step0()`

```javascript
static step0(n)
```


A stepping function, returns 1 for any positive value of `n`.




---

### `step1()`

```javascript
static step1(n)
```


A stepping function, returns 1 if `n` is greater than or equal to 1.




---

### `linear()`

```javascript
static linear(t)
```


A linear function, `f(t) = t`. Position correlates to elapsed time one to
one.

http://cubic-bezier.com/#0,0,1,1




---

### `ease()`

```javascript
static ease(t)
```


A simple inertial interaction, similar to an object slowly accelerating to
speed.

http://cubic-bezier.com/#.42,0,1,1




---

### `quad()`

```javascript
static quad(t)
```


A quadratic function, `f(t) = t * t`. Position equals the square of elapsed
time.

http://easings.net/#easeInQuad




---

### `cubic()`

```javascript
static cubic(t)
```


A cubic function, `f(t) = t * t * t`. Position equals the cube of elapsed
time.

http://easings.net/#easeInCubic




---

### `poly()`

```javascript
static poly(n)
```


A power function. Position is equal to the Nth power of elapsed time.

n = 4: http://easings.net/#easeInQuart
n = 5: http://easings.net/#easeInQuint




---

### `sin()`

```javascript
static sin(t)
```


A sinusoidal function.

http://easings.net/#easeInSine




---

### `circle()`

```javascript
static circle(t)
```


A circular function.

http://easings.net/#easeInCirc




---

### `exp()`

```javascript
static exp(t)
```


An exponential function.

http://easings.net/#easeInExpo




---

### `elastic()`

```javascript
static elastic(bounciness)
```


A simple elastic interaction, similar to a spring oscillating back and
forth.

Default bounciness is 1, which overshoots a little bit once. 0 bounciness
doesn't overshoot at all, and bounciness of N > 1 will overshoot about N
times.

http://easings.net/#easeInElastic




---

### `back()`

```javascript
static back(s)
```


Use with `Animated.parallel()` to create a simple effect where the object
animates back slightly as the animation starts.

Wolfram Plot:

- http://tiny.cc/back_default (s = 1.70158, default)




---

### `bounce()`

```javascript
static bounce(t)
```


Provides a simple bouncing effect.

http://easings.net/#easeInBounce




---

### `bezier()`

```javascript
static bezier(x1, y1, x2, y2)
```


Provides a cubic bezier curve, equivalent to CSS Transitions'
`transition-timing-function`.

A useful tool to visualize cubic bezier curves can be found at
http://cubic-bezier.com/




---

### `in()`

```javascript
static in(easing)
```


Runs an easing function forwards.




---

### `out()`

```javascript
static out(easing)
```


Runs an easing function backwards.




---

### `inOut()`

```javascript
static inOut(easing)
```


Makes any easing function symmetrical. The easing function will run
forwards for half of the duration, then backwards for the rest of the
duration.