converters.js

// Find closest index for a given value
const closest = (array, n) => array.findIndex((elem) => (n <= elem));

export function valueToPosition(value, valuesArray, sliderLength) {
  const index = closest(valuesArray, value);
  const arrLength = valuesArray.length - 1;
  const validIndex = index === -1 ? arrLength : index;

  return sliderLength * validIndex / arrLength;
}

export function positionToValue(position, valuesArray, sliderLength) {
  const max = valuesArray.length - 1 
  const min = 0
  const positionPercent = 100 * position / sliderLength;
  const minv = Math.log(1);
  const maxv = Math.log(max);

  if (positionPercent === 0) {
    return min;
  } else if (positionPercent === 100) {
    return max;
  }

  const scale = (maxv - minv) / 100;
  return Math.floor(Math.exp(minv + (scale * positionPercent))) || 0;
}

export function createArray(start, end, step) {
  var i;
  var length;
  var direction = start - end > 0 ? -1 : 1;
  var result = [];
  if (!step) {
    //console.log('invalid step: ', step);
    return result;
  } else {
    length = Math.abs((start - end) / step) + 1;
    for (i = 0; i < length; i++) {
      result.push(start + i * Math.abs(step) * direction);
    }
    return result;
  }
}