CFP - Docs - groupBy

groupBy

(toGroup: GroupingFn) => (collection: Collection) => GroupedValues

Place values of a collection into groups

Try It

const groupByFloor = groupBy(Math.floor)
const result = groupByFloor([1.2, 2.7, 1.8])
console.log(result)
// is {
//   1: [1.2, 1.8]
//   2: [2.7]
// }
const groupByFloor = groupBy(Math.floor)
const result = groupByFloor([1.2, 2.7, 1.8])
console.log(result)
// is {
//   1: [1.2, 1.8]
//   2: [2.7]
// }

Try It

const groupByFloor = groupBy(Math.floor)
const result = groupByFloor([1.2, 2.7, 1.8])
console.log(result)
// is {
//   1: [1.2, 1.8]
//   2: [2.7]
// }
const groupByFloor = groupBy(Math.floor)
const result = groupByFloor([1.2, 2.7, 1.8])
console.log(result)
// is {
//   1: [1.2, 1.8]
//   2: [2.7]
// }

Sometimes we want to place values into groups. Below, we work for a jet ski rental company. Let's split our jet skis into classes of 'beginner' and 'proficient.'

Try It

const jetSkis = [
  {
    brand: 'WaveRunner',
    mph: 45,
  },
  {
    brand: 'Sea-Doo',
    mph: 50,
  },
  {
    brand: 'Jet Ski',
    mph: 55,
  },
]

const getRecommendedExperience = jetSki => {
  return jetSki.mph < 50 ? 'beginner' : 'proficient'
}
const groupByExperience = groupBy(getRecommendedExperience)
const jetSkisByExperience = groupByExperience(jetSkis)
console.log(jetSkisByExperience)
// is {
//   beginner: [
//     { brand: 'WaveRunner', mph: 45 }
//   ],
//   proficient: [
//     { brand: 'Sea-Doo', mph: 50 }
//     { brand: 'Jet Ski', mph: 55 }
//   ],
// }
type JetSki = { brand: string; mph: number }

const jetSkis: JetSki[] = [
  {
    brand: 'WaveRunner',
    mph: 45,
  },
  {
    brand: 'Sea-Doo',
    mph: 50,
  },
  {
    brand: 'Jet Ski',
    mph: 55,
  },
]

const getRecommendedExperience = (jetSki: JetSki) => {
  return jetSki.mph < 50 ? 'beginner' : 'proficient'
}
const groupByExperience = groupBy(getRecommendedExperience)<JetSki[]>
const jetSkisByExperience = groupByExperience(jetSkis)
console.log(jetSkisByExperience)
// is {
//   beginner: [
//     { brand: 'WaveRunner', mph: 45 }
//   ],
//   proficient: [
//     { brand: 'Sea-Doo', mph: 50 }
//     { brand: 'Jet Ski', mph: 55 }
//   ],
// }

Try It

const jetSkis = [
  {
    brand: 'WaveRunner',
    mph: 45,
  },
  {
    brand: 'Sea-Doo',
    mph: 50,
  },
  {
    brand: 'Jet Ski',
    mph: 55,
  },
]

const getRecommendedExperience = jetSki => {
  return jetSki.mph < 50 ?
      'beginner'
    : 'proficient'
}
const groupByExperience = groupBy(
  getRecommendedExperience
)
const jetSkisByExperience =
  groupByExperience(jetSkis)
console.log(jetSkisByExperience)
// is {
//   beginner: [
//     { brand: 'WaveRunner', mph: 45 }
//   ],
//   proficient: [
//     { brand: 'Sea-Doo', mph: 50 }
//     { brand: 'Jet Ski', mph: 55 }
//   ],
// }
type JetSki = { brand: string; mph: number }

const jetSkis: JetSki[] = [
  {
    brand: 'WaveRunner',
    mph: 45,
  },
  {
    brand: 'Sea-Doo',
    mph: 50,
  },
  {
    brand: 'Jet Ski',
    mph: 55,
  },
]

const getRecommendedExperience = (
  jetSki: JetSki
) => {
  return jetSki.mph < 50 ?
      'beginner'
    : 'proficient'
}
const groupByExperience = groupBy(
  getRecommendedExperience
)<JetSki[]>
const jetSkisByExperience =
  groupByExperience(jetSkis)
console.log(jetSkisByExperience)
// is {
//   beginner: [
//     { brand: 'WaveRunner', mph: 45 }
//   ],
//   proficient: [
//     { brand: 'Sea-Doo', mph: 50 }
//     { brand: 'Jet Ski', mph: 55 }
//   ],
// }