easing.js

const easings = {
  linear (t, b, c, d) {
    return c * t / d + b;
  },
  easeInQuad (t, b, c, d) {
    return c * (t /= d) * t + b;
  },
  easeOutQuad (t, b, c, d) {
    return -c * (t /= d) * (t - 2) + b;
  },
  easeInOutQuad (t, b, c, d) {
    if ((t /= d / 2) < 1) return c / 2 * t * t + b;
    return -c / 2 * ((--t) * (t - 2) - 1) + b;
  },
  easeInCubic (t, b, c, d) {
    return c * (t /= d) * t * t + b;
  },
  easeOutCubic (t, b, c, d) {
    return c * ((t = t / d - 1) * t * t + 1) + b;
  },
  easeInOutCubic (t, b, c, d) {
    if ((t /= d / 2) < 1) return c / 2 * t * t * t + b;
    return c / 2 * ((t -= 2) * t * t + 2) + b;
  },
  easeInExpo (t, b, c, d) {
    return (t == 0) ? b : c * Math.pow(2, 10 * (t / d - 1)) + b - c * 0.001;
  },
  easeOutExpo (t, b, c, d) {
    return (t == d) ? b + c : c * 1.001 * (-Math.pow(2, -10 * t / d) + 1) + b;
  },
  easeInOutExpo (t, b, c, d) {
    if (t == 0) return b;
    if (t == d) return b + c;
    if ((t /= d / 2) < 1) return c / 2 * Math.pow(2, 10 * (t - 1)) + b - c * 0.0005;
    return c / 2 * 1.0005 * (-Math.pow(2, -10 * --t) + 2) + b;
  },
  easeInElastic (t, b, c, d, a, p) {
    var s;
    if (t == 0) return b;
    if ((t /= d) == 1) return b + c;
    if (!p) p = d * 0.3;
    if (!a || a < Math.abs(c)) {
      a = c;
      s = p / 4;
    } else s = p / (2 * Math.PI) * Math.asin(c / a);
    return -(a * Math.pow(2, 10 * (t -= 1)) * Math.sin((t * d - s) * (2 * Math.PI) / p)) + b;
  },
  easeOutElastic (t, b, c, d, a, p) {
    var s;
    if (t == 0) return b;
    if ((t /= d) == 1) return b + c;
    if (!p) p = d * 0.3;
    if (!a || a < Math.abs(c)) {
      a = c;
      s = p / 4;
    } else s = p / (2 * Math.PI) * Math.asin(c / a);
    return (a * Math.pow(2, -10 * t) * Math.sin((t * d - s) * (2 * Math.PI) / p) + c + b);
  },
  easeInOutElastic (t, b, c, d, a, p) {
    var s;
    if (t == 0) return b;
    if ((t /= d / 2) == 2) return b + c;
    if (!p) p = d * (0.3 * 1.5);
    if (!a || a < Math.abs(c)) {
      a = c;
      s = p / 4;
    } else s = p / (2 * Math.PI) * Math.asin(c / a);
    if (t < 1) return -0.5 * (a * Math.pow(2, 10 * (t -= 1)) * Math.sin((t * d - s) * (2 * Math.PI) / p)) + b;
    return a * Math.pow(2, -10 * (t -= 1)) * Math.sin((t * d - s) * (2 * Math.PI) / p) * 0.5 + c + b;
  },
  easeInBack (t, b, c, d, s) {
    if (s == undefined) s = 1.70158;
    return c * (t /= d) * t * ((s + 1) * t - s) + b;
  },
  easeOutBack (t, b, c, d, s) {
    if (s == undefined) s = 1.70158;
    return c * ((t = t / d - 1) * t * ((s + 1) * t + s) + 1) + b;
  },
  easeInOutBack (t, b, c, d, s) {
    if (s == undefined) s = 1.70158;
    if ((t /= d / 2) < 1) return c / 2 * (t * t * (((s *= (1.525)) + 1) * t - s)) + b;
    return c / 2 * ((t -= 2) * t * (((s *= (1.525)) + 1) * t + s) + 2) + b;
  },
  easeInBounce (t, b, c, d) {
    return c - $.easing.easeOutBounce(x, d - t, 0, c, d) + b;
  },
  easeOutBounce (t, b, c, d) {
    if ((t /= d) < (1 / 2.75)) {
      return c * (7.5625 * t * t) + b;
    } else if (t < (2 / 2.75)) {
      return c * (7.5625 * (t -= (1.5 / 2.75)) * t + 0.75) + b;
    } else if (t < (2.5 / 2.75)) {
      return c * (7.5625 * (t -= (2.25 / 2.75)) * t + 0.9375) + b;
    } else {
      return c * (7.5625 * (t -= (2.625 / 2.75)) * t + 0.984375) + b;
    }
  },
  easeInOutBounce (t, b, c, d) {
    if (t < d / 2) return $.easing.easeInBounce(x, t * 2, 0, c, d) * 0.5 + b;
    return $.easing.easeOutBounce(x, t * 2 - d, 0, c, d) * 0.5 + c * 0.5 + b;
  }
};