addimated/lib/Easing.js

An always interruptable, declarative animation library for React

import BezierEasing from "bezier-easing";
/**
 * This class implements common easing functions. The math is pretty obscure,
 * but this cool website has nice visual illustrations of what they represent:
 * http://xaedes.de/dev/transitions/
 */

var _ease = BezierEasing(0.42, 0, 1, 1);

function step0(n) {
  return n > 0 ? 1 : 0;
}

function step1(n) {
  return n >= 1 ? 1 : 0;
}

function linear(t) {
  return t;
}

function ease(t) {
  return _ease(t);
}

function quad(t) {
  return t * t;
}

function cubic(t) {
  return t * t * t;
}

function poly(n) {
  return function (t) {
    return Math.pow(t, n);
  };
}

function sin(t) {
  return 1 - Math.cos(t * Math.PI / 2);
}

function circle(t) {
  return 1 - Math.sqrt(1 - t * t);
}

function exp(t) {
  return Math.pow(2, 10 * (t - 1));
}
/**
 * A simple elastic interaction, similar to a spring.  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.
 *
 * Wolfram Plots:
 *
 *   http://tiny.cc/elastic_b_1 (default bounciness = 1)
 *   http://tiny.cc/elastic_b_3 (bounciness = 3)
 */


function elastic() {
  var bounciness = arguments.length > 0 && arguments[0] !== undefined ? arguments[0] : 1;
  var p = bounciness * Math.PI;
  return function (t) {
    return 1 - Math.pow(Math.cos(t * Math.PI / 2), 3) * Math.cos(t * p);
  };
}

function back(s) {
  if (s === undefined) {
    s = 1.70158;
  }

  return function (t) {
    return t * t * ((s + 1) * t - s);
  };
}

function bounce(t) {
  if (t < 1 / 2.75) {
    return 7.5625 * t * t;
  }

  if (t < 2 / 2.75) {
    t -= 1.5 / 2.75;
    return 7.5625 * t * t + 0.75;
  }

  if (t < 2.5 / 2.75) {
    t -= 2.25 / 2.75;
    return 7.5625 * t * t + 0.9375;
  }

  t -= 2.625 / 2.75;
  return 7.5625 * t * t + 0.984375;
}

function _in(easing) {
  return easing;
}
/**
 * Runs an easing function backwards.
 */


function out(easing) {
  return function (t) {
    return 1 - easing(1 - t);
  };
}
/**
 * Makes any easing function symmetrical.
 */


function inOut(easing) {
  return function (t) {
    if (t < 0.5) {
      return easing(t * 2) / 2;
    }

    return 1 - easing((1 - t) * 2) / 2;
  };
}

export { step0, step1, linear, ease, quad, cubic, poly, sin, circle, exp, elastic, back, bounce, BezierEasing as bezier, _in as in, out, inOut };
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