d3-interpolate.js

const linearInterpolate = interpolateObject({ val: 0 }, { val: 100 })
console.log(linearInterpolate(0.25))
console.log(linearInterpolate(0.75))

const easeInterpolate = easeFn => (a, b) => {
  const i = interpolateObject(a, b)
  return t => i(easeFn(t))
}
const curvedInterpolate = easeInterpolate(easeQuadInOut)({ val: 0 }, { val: 100 })
console.log(curvedInterpolate(0.25))
console.log(curvedInterpolate(0.75))

// one liner:
// const easeInterpolate = easeFn => (a, b) => t => interpolateObject(a, b)(easeFn(t))