Scales a number expected to be in the range [inMin-inMax] to a number in the range [outMin-outMax].

rangeTransform.ts

/**
  Scales a number expected to be in the range [inMin-inMax]
  to a number in the range [outMin-outMax]

  eg:
  rangeTransform(5, [0, 10], [0, 50])
  > 25

  NOTE: If num is outside of [inMin-inMax] the result will
        also be outside [outMin-outMax].
*/
export default function rangeTransform(
  num: number,
  [inMin, inMax]: Tuple,
  [outMin, outMax]: Tuple
) {
  const rebase = num - inMin
  const desiredRange = outMax - outMin
  const inputRange = inMax - inMin
  const scalingFactor = desiredRange / inputRange
  return rebase * scalingFactor + outMin
}

type Tuple = [number, number]