# 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 animationsβ

The `Easing`

module provides several predefined animations through the following methods:

`back`

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

provides a bouncing animation`ease`

provides a basic inertial animation`elastic`

provides a basic spring interaction

### Standard functionsβ

Three standard easing functions are provided:

The `poly`

function can be used to implement quartic, quintic, and other higher power functions.

### Additional functionsβ

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

## Exampleβ

# Reference

## Methodsβ

`step0()`

β

`static step0(n)`

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

.

`step1()`

β

`static step1(n)`

A stepping function, returns 1 if `n`

is greater than or equal to 1.

`linear()`

β

`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()`

β

`static ease(t)`

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

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

`quad()`

β

`static quad(t)`

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

. Position equals the square of elapsed time.

http://easings.net/#easeInQuad

`cubic()`

β

`static cubic(t)`

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

. Position equals the cube of elapsed time.

http://easings.net/#easeInCubic

`poly()`

β

`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()`

β

`static sin(t)`

A sinusoidal function.

http://easings.net/#easeInSine

`circle()`

β

`static circle(t)`

A circular function.

http://easings.net/#easeInCirc

`exp()`

β

`static exp(t)`

An exponential function.

http://easings.net/#easeInExpo

`elastic()`

β

`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()`

β

`static back(s)`

Use with `Animated.parallel()`

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

`bounce()`

β

`static bounce(t)`

Provides a basic bouncing effect.

http://easings.net/#easeInBounce

`bezier()`

β

`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()`

β

`static in easing;`

Runs an easing function forwards.

`out()`

β

`static out(easing)`

Runs an easing function backwards.

`inOut()`

β

`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.