getProgress.js

import EASINGS from './easings';
import getScrollTo from './bezier';

const getProgress = ({
  easingPreset, 
  cubicBezierPoints,
  duration,
  runTime
}) => {
  const percentTimeElapsed = runTime / duration;

  if (EASINGS.hasOwnProperty(easingPreset)) {
    return EASINGS[easingPreset](percentTimeElapsed);
  } else if (
    cubicBezierPoints
    && !isNaN(cubicBezierPoints.x1) 
    && !isNaN(cubicBezierPoints.y1) 
    && !isNaN(cubicBezierPoints.x2) 
    && !isNaN(cubicBezierPoints.y2)
    && cubicBezierPoints.x1 >= 0
    && cubicBezierPoints.x2 >= 0) {
    return getScrollTo({
      percentTimeElapsed,
      'x1': cubicBezierPoints.x1,
      'x2': cubicBezierPoints.x2,
      'y1': cubicBezierPoints.y1,
      'y2': cubicBezierPoints.y2
    });    
  } else {
    console.error('Please enter a valid easing value');
  }
  return false;
}