Easers

A set of composable easing functions.

Installation

npm install --save @porkchopsandwich/easers

Use

import { linear, cubic, inverse } from "@porkchopsandwich/easers";

// Basic easers take an X value between 0 and 1, and return the matching Y value.
const y = linear(0.3); // => 0.3

// Other easers are higher order functions that operate on other easers
const invertedLinear = inverse(linear);
const y2 = invertedLinear(0.3);

Available easers

linear(x) => y

Returns the passed X as Y.

fixedFactory(x) => () => y

Returns an easer that always returns the initial value.

sineWaveFactory(amplitude = 1, ordinaryFrequency = 1, phase = 0) => (x) => y

Returns an easer that models a sine wave.

circular(x) => y

Models a circular easing.

exponential(x) => y

Models an exponential easing.

powerFactory(power = 1) => (x) => y

Returns an easer that models the passed power easing.

squared(x) => y

cubed(x) => y

quad(x) => y

Convenience easers for powers of 2, 3 and 4.

bounceFactory(baseline = 2.75) => (x) => y

Returns a 'bounce' easer (based on Robert Penner's easing methods: http://robertpenner.com/easing/)

elastic(x) => y

Models an elastic easer (based on Robert Penner's easing methods: http://robertpenner.com/easing/)

doubleArcFactory(max = 1.1) => (x) => y

Returns an easer that models a double arc.

Higher Order Easers

reverse(easer) => (x) => y

Returns an easer that flips the X value passed to the easer (1 to 0 rather than 0 to 1)

mirror(easer) => (x) => y

Returns an easer whose which produces a mirrored pair of the easer.

inverse(easer) => (x) => y

Returns an easer that flips the X value passed to the easer, AND flips the returned Y value. Effectively mirrors the easer on a diagonal.

pair(easer1, easer2) => (x) => y

Returns an easer that invokes easer1 for the first half of the X range, and easer2 for the second half.

inOut(easer) => (x) => y

Returns an easer that invokes easer normally for the first half of the X range, and the inverse of easer for the second half.

mean(...easers) => (x) => y

Returns an easer that returns the mean value returned by all the input easers.

sequence(...easers) => (x) => y

Returns an easer that breaks up the X value into a set matching the length of the input easers, and calls the appropriate one for the supplied X value.

set(...easerSets) => (x) => y

Easer Sets are a 3-tuples consisting of an easer, a start x and an end x. Returns an easer that returns the mean of all easers whose set starts before the input X and ends after the input X.

Utilities

toRange(x, min = 0, max = 1) => y

Converts a value between 0 and 1 to one on a range between min and max.

arrayMean(arrayOfNumbers) => y

Returns the average of all numbers in an array.