Program.js

program.js

const ANIMALS = [
  {
    date: '2019-02-10',
    location: 'A',
    code: 1,
  },
  {
    date: '2019-03-17',
    location: 'B',
    code: 15,
  },
  {
    date: '2019-03-17',
    location: 'A',
    code: 45,
  },
  {
    date: '2019-03-17',
    location: 'A',
    code: 354,
  },
  {
    date: '2019-03-17',
    location: 'B',
    code: 34535,
  },
  {
    date: '2019-03-17',
    location: 'A',
    code: 345,
  },
  {
    date: '2019-03-17',
    location: 'B',
    code: 1001,
  },
]

function MammalsPercentage(animals) {
  //we save the animal array length
  //we calcule the length of the array once
  let lengthJson = animals.length
  let mammalAnimal = 0
  let mammalsPercentage
  animals.forEach(animal => {
    if (animal.code > 1000) {
      mammalAnimal++
    }
  })
  // we calcule the percentage of mammal animals
  mammalsPercentage = (mammalAnimal * 100) / lengthJson
  // we print in console the number of mammal animals (whose code above 1000)
  console.log(mammalsPercentage + ' %')
}

function OftenMammalDay(animals) {
  //we save the animal array length

  //date more repeated in location A and with different code
  let daySelected
  let mammalsPercentage
  //we apply a filter to get an array just located in place A
  let animalsLocA = animals.filter(
    animalLocationA => animalLocationA.location === 'A'
  )
  // we make an auxiliar copy of array AnimalsLocA to check both arrays and detect the repeated
  let animalsLocACopy = animalsLocA
  animalsLocA.forEach(animal => {
    animalsLocACopy.forEach(animalCopy => {
      //
      if (animal.date === animalCopy.date) {
        daySelected = animal.date
      }
    })
  })
  console.log(daySelected)
}

MammalsPercentage(ANIMALS)
OftenMammalDay(ANIMALS)