# 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:

### Standard functions

Three standard easing functions are provided:

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

Additional mathematical functions are provided by the following methods:

The following helpers are used to modify other easing functions.

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

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

### `quad()`

``````
``````

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

### `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.

### `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 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()`

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

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

### `bounce()`

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

Provides a simple 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.