Example of Functional Programming composition funciton with TypeScript Generics

fp-composition-generics.ts

interface IMealCategory {
  id: number
  key: 'desert' | 'slow-cook' | 'breakfast' | 'protein'
}

const getMealCategoryBy = <T extends IMealCategory, K extends keyof IMealCategory>(mealCategories: T[], by: K) => {
  return (value: T[K]) => {
    return mealCategories.find((mealCategory) => {
      return mealCategory[by] === value
    })
  }
}

const mealCategories: IMealCategory[] = [
  {
    id: 1,
    key: 'desert'
  },
  {
    id: 2,
    key: 'breakfast'
  },
  {
    id: 3,
    key: 'protein'
  }
]

const getMealCategoryByKey = getMealCategoryBy(mealCategories, 'key')
const getMealCategoryById = getMealCategoryBy(mealCategories, 'id')

console.log(getMealCategoryByKey('breakfast'))
console.log(getMealCategoryByKey('desert'))
console.log(getMealCategoryById(1))
console.log(getMealCategoryById(2))