recursiveInterpolation in javascript

recursiveInterpolation.js

function interpolatedPairs (array) {
	return array.slice(0, array.length - 1).map((v, i) => [v, interpolate(v, array[i + 1])])
}

function interpolate(a, b) {
	return (a + b) / 2
}

function flatten (arr) {
	return arr.reduce((acc, v) => acc.concat(v), [])
}

function interpolatedArray (array) {
	return flatten(interpolatedPairs(array)).concat(array.slice(-1))
}

function recursiveInterpolation (arr, i) {
	return i === 1 ? interpolatedArray(arr) : recursiveInterpolation(interpolatedArray(arr), i - 1)
}