KathyPuma / array_methods_assignment

Exercises

1. Given an array of numbers, write a function that returns a new array where every element is incremented by 10.

Input: [1,2,3,4,5]
Output: [11,12,13,14,15]

2. Given an array, return a new array where every non-string element is converted to an empty string.

Input: ["a", 123, "b", "c", {name: "cat"}]
Output: ["a", "", "b", "c", ""]

3. Write a function that returns only the even elements in an array of numbers.

Input: [1,2,3,4,5]
Output: [2,4]

4. Write a function that checks if all elements in the array are the same.

Input: [1,1,1,1,1]
Output: true

Input: [1,1,1,1,2]
Output: false

5. Write a function that returns the sum of every element in an array.

Input: [1,2,3,4,5]
Output: 15

6. Write a function that finds largest number in an array.

Input: [1,2,6,3,4,5]
Output: [6]

7. Write a function countZeroes, which takes an array of numbers as its argument and returns the amount of zeroes that occur in it.

Input: [1,0,0,2,0,3,0,0,0]
Output: 6

8. Write a function that doubles every element in an array.

Input: [1,2,3,4]
Output: [2,4,6,8]

9. Write a function that finds the sum of every element in an array doubled

Input: [1,2,3,4]
Output: 20

10. Write a function elementDivisibleBy with parameters divisor and arr. Return a new array of every element of arr that can be evenly divided by divisor.

Input: 5, [4,5,6,7,8,9,10,11,12,13,14,15]
Output: [5,10,15]

11. Write a numberTimesIdx that uses map and multiples each number in the array by its index.

Input: [6,7,8,9]
Output: [0,7,16,27]

12. Write a function that returns whether or not every value in an array is a positive even number that doesn't end in 0.

Input: [2,4,6,8,12]
Output: true

Input: [2,4,6,8,10]
Output: false

13. Write a function that returns the sum of all odd numbers in an Array

Hint: What is the second argument in reduce?

Input: [2,3,4,5]
Output: 8

Input: [1,2,3,4,5]
Output: 9

14. Write a function that returns a new array containing all of the strings in the original array uppercased.

Input: [{}, 1, "cat", 3, ["hi"], {name: "dog"}, "dog", "bear"]
Output: ["CAT", "DOG", "BEAR"]

Bonus:

You can write your own array methods!

Array.prototype.sayHi = function() {
  console.log("Hi")
}

Now every array that you write has a sayHi method that you can call.

let myArr = [1,2,3]
myArr.sayHi() //Logs "Hi" to the console

1. Using Array.prototype add a new method myForEach that mimics the behavior of the built in forEach.

2. Use your myForEach to add myMap to the Array prototype. myMap should behave the same as regular map.

3. Write a myFilter that behaves the same as filter.

4. Write a myEvery that behaves the same as every.

5. Write a myReduce. It should use the first element in the array if none is given.

6. Write a myJoin function.

7. Write a mySlice function.

8. Write a myTranspose. This function should transpose a matrix.

let mtx = [
            [1, 2],
            [3, 4],
            [5, 6]
          ]

mtx.myTranspose();

// => [
        [1, 3, 5],
        [2, 4, 6]
       ]

9. Write a myFlatten. This should take a multi-dimensional array and return it as one array.

let arr = [1, 2, [3, 4, 5, [6, 7, 8]]]
  arr.myFlatten();
  // => [1, 2, 3, 4, 5, 6, 7, 8]