# Easing

The `Easing`

module implements common easing functions. This module is used by Animated.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`

provides an animation where the object goes slightly back before moving forward`bounce`

provides a bouncing animation`ease`

provides an inertial animation`elastic`

provides a basic spring interaction

### Standard functions

Three standard easing functions are provided:

The `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`

provides a cubic bezier curve`circle`

provides a circular function`sin`

provides a sinusoidal function`exp`

provides an exponential function

The following helpers are used to modify other easing functions.

`in`

runs an easing function forwards`inOut`

makes any easing function symmetrical`out`

runs an easing function backwards

### Methods

# Reference

## Methods

`step0()`

```
static step0(n)
```

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

.

`step1()`

```
static step1(n)
```

A stepping function, returns 1 if `n`

is greater than or equal to 1.

`linear()`

```
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()`

```
static ease(t)
```

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

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

`quad()`

```
static quad(t)
```

A quadratic function, `f(t) = t * t`

. Position equals the square of elapsed time.

http://easings.net/#easeInQuad

`cubic()`

```
static cubic(t)
```

A cubic function, `f(t) = t * t * t`

. Position equals the cube of elapsed time.

http://easings.net/#easeInCubic

`poly()`

```
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()`

```
static sin(t)
```

A sinusoidal function.

http://easings.net/#easeInSine

`circle()`

```
static circle(t)
```

A circular function.

http://easings.net/#easeInCirc

`exp()`

```
static exp(t)
```

An exponential function.

http://easings.net/#easeInExpo

`elastic()`

```
static elastic(bounciness)
```

A basic 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()`

```
static back(s)
```

Use with `Animated.parallel()`

to create an effect where the object animates back slightly as the animation starts.

`bounce()`

```
static bounce(t)
```

Provides a bouncing effect.

http://easings.net/#easeInBounce

`bezier()`

```
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()`

```
static in easing;
```

Runs an easing function forwards.

`out()`

```
static out(easing)
```

Runs an easing function backwards.

`inOut()`

```
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.