JavaScript Iterators

Open a Repl to do the following exercises. Submit your REPL link to the Project Submission Doc.

.forEach()

• getCounter – counts how many of each charater are in a string and returns in an object

  • ex: getCounter('mom') => {m: 2, o: 1}
  • ex: getCounter('caterpillar') => {c: 1, a: 2, t: 1, e: 1, r: 2, i: 1, l: 2}

• countIntegers – counts how many integers there are in an array

  • ex: countIntegers([4, 2.2, 5, 6, 4.2, 8.2, 4]) // => 4
  • Hint: Google how you can check if a number is an integer in JavaScript

• sumIsDivisibleBy5 – adds all numbers in an array and returns if the sum is divisible by 5

  • ex. sumIsDivisibleBy5([1, 2, 3, 4, 5]) // => true (bc 1 + 2 + 3 + 4 + 5 = 15, and 15 is divisible by 5)
  • Hint: define var totalSum = 0; in the beginning, and remember what modulus does

• getPersonSentence – formats an object (with name, yearOfBirth, and city keys) into a sentence

  • ex. getPersonSentence({name: ’Sam’, yearOfBirth: 1990, city: 'Los Angeles'}) // => 'Sam is 28 years old and lives in Los Angeles'
  • Hint: Google how you can get the current year in JavaScript (without hard-coding in var currentYear = 2018)

• getLongestName – takes in an array of objects (with name and age keys), and prints out the longest name

  • ex: getLongestName([{name: ’Sam’, age: 20}, {name: ’Charlotte’, age: 30}, {name: ’Dany’, age: 40}]) => ‘Charlotte’

.map()

Write code using .map() to have the following input and output:

• getSquares – takes in an array of numbers and returns an array of their squares

  • ex: getSquares([1, 2, 3, 4, 5]) => [1, 4, 9, 16, 25]

• isDivisibleBy3 – takes in an array of numbers and returns an array of booleans indicating whether each element is divisible by 3

  • ex: isDivisibleBy3[1, 3, 4, 6, 7, 8, 9] => [false, true, false, true, false, false true]

• getColors – takes in an array of objects (with name and color keys) and returns an array of each object’s color

  • ex: getColors([{name: ’apple’, color: 'red'}, {name: ’banana’, color: 'yellow'}, {name: ’kiwi’, color: 'green'}]) => ['red', 'yellow', 'green']

• getCities – takes in an array of objects (with city and state keys) and returns an array of each object’s city

  • ex: getNames([{city: ’Nashville’, state: 'Tennessee'}, {city: ’Portland’, state: 'Maine'}, {city: ’New York City’, state: 'New York'}]) => ['Nashville', 'Portland', 'New York City']

.filter()

Write code using .filter() to have the following input and output:

• getOdds – takes in an array of numbers and returns an array of only odd numbers

  • ex: getOdds([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]) => [1, 3, 5, 7, 9]

• getEvens – takes in an array of numbers and returns an array of only even numbers

  • ex: getEvens([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]) => [2, 4, 6, 8, 10]

• getDivisibleBy4 – takes in an array of numbers and returns an array of only numbers that are divisible by 4

  • ex: getDivisibleBy4([1, 4, 6, 8, 12, 13]) => [4, 8, 12]

• getCWords – takes in an array of words and returns an array of only words that start with C (uppercase OR lowercase)

  • ex: getCWords(['Carl', 'Allie', 'Ben', 'car', 'Carmen']) => ['Carl', 'car', 'Carmen']

• getSquares – takes in an array of numbers and returns an array of only numbers that have an integer square root

  • ex: getSquares([1, 2, 4, 6, 7, 9, 12, 16, 20, 25]) => [1, 4, 9, 16, 25]
  • Hint: Figure out how to get the square root of each number, then test if that square root is an integer

• getCNamedObjects – takes in an array of objects and returns an array of only objects with a nam that start with C (uppercase OR lowercase)

  • ex: getCNamedObjects([{name: 'Carl', age: 30}, {name: 'Allie', age: 20}, {name: 'Ben', age: 40}, {name: 'Cara', age: 10}, {name: 'Carmen', age: 15}]) => [{name: 'Carl', age: 30}, {name: 'Cara', age: 10}, {name: 'Carmen', age: 15}]
  • Hint: Look at your previously written getCWords function for some inspiration

.reduce()

Write code using .reduce() to have the following input and output:

• addUpAll – add up all numbers in a given array

  • ex. addUpAll([1, 2, 3, 4, 5, 6, 7, 8, 9, 10]) => 55

• multiplyAllNums – multiply all numbers in a given array

  • ex. multiplyAllNums([1, 2, 3, 4, 5]) => 120

• squareAllNums – power up all numbers in a given array

  • ex. squareAllNums([3, 2, 3]) => 729, bc (3 ^ 2) = 9, and (9 ^ 3) = 729

• addUpAllAges – add up all the ages in an array of objects

  • ex. addUpAllAges([{name: 'Carl', age: 30}, {name: 'Cara', age: 10}, {name: 'Carmen', age: 15}]) => 55