CFP - Docs - lessThan

lessThan

(right: number) => (left: number) => number

Test whether a number is less than another

Try It

const lt2 = lessThan(2)
lt2(1) // is true
lt2(2) // is false
const lt2 = lessThan(2)
lt2(1) // is true
lt2(2) // is false

Try It

const lt2 = lessThan(2)
lt2(1) // is true
lt2(2) // is false
const lt2 = lessThan(2)
lt2(1) // is true
lt2(2) // is false

Sometimes we want to test for thresholds. Below, we run a scooter company. Users rate the scooters after use, allowing us to inspect those that don't operate smoothly. Let's get the scooters that are rated less than 4 stars.

Try It

const scooterRatings = {
  s52: 3.4,
  s14: 4.0,
  s67: 3.8,
}

const lessThan4Stars = lessThan(4)
const getScootersToInspect = compose([keepWhen(lessThan4Stars), Object.keys])

const scooterIds = getScootersToInspect(scooterRatings)
console.log(scooterIds)
// [
//   s52
//   s67
// ]
type Ratings = Record<string, number>
const scooterRatings: Ratings = {
  s52: 3.4,
  s14: 4.0,
  s67: 3.8,
}

const lessThan4Stars = lessThan(4)
const getScootersToInspect = compose([
  keepWhen(lessThan4Stars)<Ratings>,
  Object.keys,
])

const scooterIds = getScootersToInspect(scooterRatings)
console.log(scooterIds)
// [
//   s52
//   s67
// ]

Try It

const scooterRatings = {
  s52: 3.4,
  s14: 4.0,
  s67: 3.8,
}

const lessThan4Stars = lessThan(4)
const getScootersToInspect = compose([
  keepWhen(lessThan4Stars),
  Object.keys,
])

const scooterIds = getScootersToInspect(
  scooterRatings
)
console.log(scooterIds)
// [
//   s52
//   s67
// ]
type Ratings = Record<string, number>
const scooterRatings: Ratings = {
  s52: 3.4,
  s14: 4.0,
  s67: 3.8,
}

const lessThan4Stars = lessThan(4)
const getScootersToInspect = compose([
  keepWhen(lessThan4Stars)<Ratings>,
  Object.keys,
])

const scooterIds = getScootersToInspect(
  scooterRatings
)
console.log(scooterIds)
// [
//   s52
//   s67
// ]