# Easing

`Easing`模块实现了常见的动画缓动函数。 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/

### 查看预置动画#

`Easing`模块通过以下几个方法提供了几种预置的动画：

### 查看标准函数#

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

### 查看补充函数#

The following helpers are used to modify other easing functions.

# 文档

## 方法#

### `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()`#

``static quad(t)``

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.