Awesome

ease

Easing functions (for canvas etc)

linear
inQuad
outQuad
inOutQuad
inCube
outCube
inOutCube
inQuart
outQuart
inOutQuart
inQuint
outQuint
inOutQuint
inSine
outSine
inOutSine
inExpo
outExpo
inOutExpo
inCirc
outCirc
inOutCirc
inBack
outBack
inOutBack
inBounce
outBounce
inOutBounce
inElastic
outElastic
inOutElastic

Aliases

in-quad
out-quad
in-out-quad
in-cube
out-cube
in-out-cube
in-quart
out-quart
in-out-quart
in-quint
out-quint
in-out-quint
in-sine
out-sine
in-out-sine
in-expo
out-expo
in-out-expo
in-circ
out-circ
in-out-circ
in-back
out-back
in-out-back
in-bounce
out-bounce
in-out-bounce
in-elastic
out-elastic
in-out-elastic

Example

var ease = require('ease');
var requestAnimationFrame = require('raf');
var canvas = document.querySelector('canvas');
var ctx = canvas.getContext('2d');

var stop = false;
function animate() {
  if (stop) return;
  requestAnimationFrame(animate);
  draw();
}

var startx = 20;
var x = startx;
var destx = 300;
var y = 400 / 2;
var duration = 1000;
var start = Date.now();
var end = start + duration;

function draw() {
  var now = Date.now();
  if (now - start >= duration) stop = true;
  var p = (now - start) / duration;
  val = ease.inOutBounce(p);
  x = startx + (destx - startx) * val;
  canvas.width = canvas.width;
  ctx.fillStyle = 'red';
  ctx.arc(x, y, 10, 0, Math.PI * 2, false);
  ctx.fill();
}

animate();

Special Thanks

These easing functions were originally written by Robert Penner, and optimized by the tween.js authors.

License

The MIT License

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.