js-arrays.md

Arrays

1. Write a function largest which returns the largest element in an array of numbers.

2. Write a function trim which returns a copy of an array removing the elements at the beginning or end that are null.

3. Write a function arraySum which returns the sum of the elements in an array.

4. Write a program that produces the sum of each column in a CSV file. To read the file:

   const fs = require("fs");
   let fileContent = fs.readFileSync("some_data.csv").toString();

5. Write a function countAppearances which receives an array of strings A (a list of words) and a string w (a single word), and returns how many times w appears in A.

6. Write a function reverse which receives an array and returns a new array with the same elements in reverse order. If the input array is [1, 2, 3, 4, 5], the function should return [5, 4, 3, 2, 1].

7. Write a function aboveAverage that receives an array of numbers and returns the fraction (between 0.0 and 1.0) of numbers in the array the are greater than the average of the array.

8. Write a function firstNonRepeated that receives a string like "aabbcdddeffgh" and returns the first letter in the string which doesn't have consecutive repetitions (in the example would be e).

9. In the game of Fizz Buzz, kids take turns in saying the natural numbers, but when a number is divisible by 3, they say "Fizz", when the number is divisible by 5 they say "Buzz", and when the number is divisible by 3 and 5 they say "Fizz Buzz". If you put the consecutive responses (either an integer or a string) in an array it would look like:

   [
     1,
     2,
     "Fizz",
     4,
     "Buzz",
     "Fizz",
     7,
     8,
     "Fizz",
     "Buzz",
     11,
     "Fizz",
     13,
     14,
     "FizzBuzz" /* ... */,
   ];

   Write a function that receives an integer length N as a parameter and produces the FizzBuzz array of length N.

10. Write a function range(a, b) that receives two integers and produces an array with the consecutive numbers starting at a but excluding b. For instance, range(4, 10) produces [4, 5, 6, 7, 8, 9].

11. Write a function that receives an array of arrays of numbers, such as [[1, 2, 3], [100, 10], [-5, -7]] and returns an array with the minimum values in each array, that is: [1, 10, -7].

12. Write a function duplicate which receives an array and an integer n and returns a new array with n concatenated copies of the original array.

13. Write a function that receives two arrays A and B and returns an array with the elements in A that are not present in B.

14. Write a function that receives two strings and returns true if they are anagrams. Two Spanish words that are anagrams are "esponja" and "japones" (accents/tildes are not taken into account).

15. Write a function that receives a string and reverses the order of all the vowels in the string: reverseVowels("I love burritos") gives "o livu berrotIs.

16. Given an array of integers (let's call it x), calculate the percentage for the number of positive integers, negative integers, and zeros in x.

17. Write a function that receives an array of numbers, and returns the median.