Preparing for the Rithm School Timed Coding Challenge

Congratulations on making it through the JavaScript fundamentals material! It's time to practice a bit with some more problems to make sure you're ready to continue learning more.

To best prepare for the Rithm School interview, make sure that you can solve each of these functions. You can also download a zip file with all of these functions and an HTML file that you can open to run automated tests to ensure you have solved the problem correctly.

Download a zip file containing tests and practice problems here

Walkthrough video for download and testing

The video below will walk you through the steps outlined on this page - from downloading the zip file, opening them in your code editor, and running the tests to ensure you've found working solutions to the practice problems!

Running the tests for each practice problem

Once you download the zip file containing the tests and practice problems, unzip the file and take a look at the contents of the folder. You will see that there is a JavaScript file for each problem that you need to solve.

You will also see that there is a readme.md file which contains instructions for each problem (you can also find these instructions below).

To make sure that you have solved each problem correctly, there is a file called tests.js which contain automated tests that will let you know if your solution is correct. Do not modify any code inside here, you do not need to write any tests yourself! To run these tests, open up the index.html file in a browser and when you do, you will see a series of red Xs which indicate that tests are failing.

When you open the index.html file, we recommend you click on the Spec List so that you can see each function and the tests associated with it. From there, you can click on an individual function to see only the tests for that specific function.

Once you have solved the problem correctly, the tests will pass and you will see green text instead of red.

We also recommend clicking on the Options button and unchecking the box for "run tests in random order".

Each of the tests check the example input and output that we provide for each problem, so if a test is failing, try the examples we provide for each function to make sure they are all working.

How to work through the practice problems

Before continuing to the list of problems, it's essential you develop some good habits around programming and practicing problem solving.

• Don't start coding right away, take some time to write down your thoughts and problem solving process
• Do not look at the solution before solving the problem!
• Make sure to run the tests for each practice problem.

Next Steps for Our Full Time Program

Once you've finished these problems, you'll be ready to take our timed coding challenge! If you have not yet, fill out the application form and we'll send you an email with next steps and the challenge!

Good luck!

appendToString

The function should return a new string which consists of the second string appended to the first string.

Examples:

appendToString("Hello", " World!"); // "Hello World!"
appendToString("Foo", "bar"); // "Foobar"
appendToString("bar", "Foo"); // "barFoo"
appendToString("", "test"); // "test"
appendToString("other test", ""); // "other test"

prependToString

Write a function called prependToString, which accepts two strings.

The function should return a new string with the second string prepended to the first string.

Examples:

prependToString('awesome', 'very') // 'veryawesome'
prependToString('world', 'hello ') // 'hello world'
prependToString('nothing', '') // 'nothing'

charAt

Write a function called charAt which accepts a string and an index (number) and returns the character at that index.

The function should return an empty string if the number is greater than the length of the string.

Do not use the built in charAt method

Examples:

charAt('awesome', 2) // 'e'
charAt('awesome', 12) // ''

stringIncludes

Write a function called stringIncludes, which accepts two strings: the first string is a word and the second string is a single character.

The function should return true if the first string includes the character, otherwise it should return false.

Do not use the built in String.includes() function!

Examples:

stringIncludes('awesome', 'e'); // true
stringIncludes('awesome', 'z'); // false

stringIndexOf

Write a function called stringIndexOf, which accepts two strings: the first is a word and the second is a single character.

The function should return the first index in the word at which the character exists or -1 if the character is not found.

Do not use the built in "string".indexOf() function!

Examples:

stringIndexOf('awesome', 'e') // 2
stringIndexOf('awesome', 'z') // -1

stringLastIndexOf

Write a function called stringLastIndexOf, which accepts two strings: the first is a word and the second is a single character.

The function should return the last index at which the character exists or -1 if the character is not found.

Do not use the built in "string".lastIndexOf() function!

Examples:

stringLastIndexOf('awesome', 'e'); // 6
stringLastIndexOf('awesome', 'z'); // -1

repeat

Write a function called repeat, which accepts a string and a number and returns a new string with the string repeated that number of times.

Do not use the built in repeat method

Examples:

repeat('Matt', 3) // 'MattMattMatt'
repeat('Elie', 2) // 'ElieElie'
repeat('Michael', 0) // ''

removeFromString

Write a function called removeFromString, which accepts a string, a starting index (number) and a number of characters to remove.

The function should return a new string with the characters removed.

Examples:

removeFromString('Elie', 2, 2) // 'El'
removeFromString('Elie', 0, 1) // 'lie'
removeFromString('Rithm School', 0, 6) // 'School'
removeFromString('Rithm School', 2, 4) // 'RiSchool'
removeFromString('Rithm School', 6, 400) // 'Rithm '

includes

Write a function called includes which accepts a collection, a value, and an optional starting index. The function should return true if the value exists in the collection when we search starting from the starting index. Otherwise, it should return false.

The collection can be a string, an array, or an object. If the collection is a string or array, the third parameter is a starting index for where to search from. If the collection is an object, the function searches for the value among values in the object; since objects have no sort order, the third parameter is ignored.

Examples:

includes([1, 2, 3], 1) // true
includes([1, 2, 3], 1, 2) // false
includes([1, 2, 3], 6) // false

includes({ 'a': 1, 'b': 2 }, 1) // true
includes({ 'a': 1, 'b': 2 }, 'a') // false

includes('abcd', 'b') // true
includes('abcd', 'e') // false
includes('abcd', 'a', 2) // false

indexOf

Write a function called indexOf, which accepts an array and a number.

The function should return the first index at which the value exists or -1 if the value is not found.

Do not use the built in Array.indexOf() function!

Examples:

let arr = [5, 10, 15, 20];
indexOf(arr, 20); // 3

let arr2 = [1, 2, 3, 4, 5];
indexOf(arr2, 2); // 1

let arr3 = [1, 2];
indexOf(arr3, 10); // -1

lastIndexOf

Write a function called lastIndexOf, which accepts an array and a number.

The function should return the last index at which the value exists, or -1 if the value is not found.

Do not use the built in Array.lastIndexOf() function!

Examples:

lastIndexOf([1, 2, 3, 4], 2); // 1
lastIndexOf([1, 2, 3, 4, 2], 2); // 4
lastIndexOf([1, 2, 3, 4], 22); // -1

max

Write a function called max, which accepts an array and returns the highest value.

Do not use the built-in Math.max() function!

Examples:

max([5, 1, 4, 7, 1, 2]); // 7
max([3, 4, 12, 1, 8]); // 12
max([-1, 6, 3, 2.2, -10, -4]); // 6

min

Write a function called min, which accepts an array of numbers and returns the lowest value.

Do note use the built-in Math.min() function!

Examples:

min([5, 1, 4, 7, 1, 2]); // 1
min([-1, 6, 3, 2.2, -10, -4]); // -10

slice

Write a function called slice, which accepts an array, and two numbers.

The function should return a new array with the elements starting at the index of the first number and going until the index of the second number.

If a third parameter is not passed to the function, it should slice until the end of the array by default.

If the third parameter is greater than the length of the array, it should slice until the end of the array.

Do not use the built in Array.slice() function!

Examples:

slice([1, 2, 3, 4, 5], 0, 2); // [1, 2]
slice([1, 2, 3, 4, 5], 2, 4); // [3, 4]
slice([1, 2, 3, 4, 5], 2); // [3, 4, 5]
slice([1, 2, 3, 4, 5], 2, 10); // [3, 4, 5]

countValues

Write a function called countValues which accepts an array and a number and returns the number of times that value appears in the array.

Examples:

countValues([4,1,4,2,3,4,4], 4) // 4
countValues([4,1,4,2,3,4,4], 100) // 0
countValues([], 1) // 0

keys

Write a function called keys, which accepts an object and returns an array of all of the keys in the object.

Do not use the built in Object.keys() function!

Examples:

let obj = { a: 1, b: 2, c: 3 };
keys(obj); // ["a", "b", "c"]

let obj2 = { first: 'Matt', last: 'Lane' };
keys(obj2); // ["first", "last"]

let obj3 = {};
keys(obj3); // []

values

Write a function called values, which accepts an object and returns an array of all of the values in the object.

Do not use the built in Object.values() function!

Examples:

let obj = { a: 1, b: 2, c: 3 };
values(obj); // [1,2,3]

let obj2 = { first: 'Matt', last: 'Lane', isDogOwner: true };
values(obj2); // ["Matt", "Lane", true]

let obj3 = {};
values(obj3); // []

squareEvenNumbers

Write a function called squareEvenNumbers which accepts an array and returns the sum of the squares of all the even numbers in the array.

Examples:

squareEvenNumbers([1, 2, 3, 4, 5]); // 20
squareEvenNumbers([1, 3, 5, 7]); // 0
squareEvenNumbers([5, 6, 7]); // 36

entries

Write a function called entries, which accepts an object and returns an array of arrays of key-value pairs.

In other words, each sub-array is an "entry" in the object with two elements: the first element is the key, and the second element is the value.

Do not use the built in Object.entries() function!

Examples:

let obj = { a: 1, b: 2, c: 3 };
entries(obj);
// [["a",1], ["b",2], ["c",3]]

let obj2 = { first: 'Matt', last: 'Lane', isDogOwner: true };
entries(obj2);
// [["first","Matt"], ["last","Lane"], ["isDogOwner",true]]

let obj3 = {};
entries(obj3); // []

multiples

Implement a function called multiples that accepts two numbers: x and n.

The function should return the first n multiples of the number x.

Assume that x is a positive integer.

Examples:

multiples(3, 4) // [3, 6, 9, 12]
multiples(2, 5) // [2, 4, 6, 8, 10]

pluck

Write a function called pluck, which takes an array of objects and the name of a key.

The function should return an array containing the value associated with that key for each object, or undefined if that key is not present in the object.

Examples:

pluck([
  { name: "Tim" }, { name: "Matt" }, { name: "Elie" }],
 'name'
)
// ["Tim", "Matt", "Elie"]

pluck(
  [{ name: "Tim", isBoatOwner: true }, { name: "Matt", isBoatOwner: false }, { name: "Elie" }],
 'isBoatOwner'
)
// [true, false, undefined]

twoHighest

Write a function called twoHighest that takes an array of numbers as its argument and returns the two highest numbers within the array.

The returned value should be an array in the following format: [secondHighest, highest]

The order of the numbers passed in could be any order.

Do not use the build in sort() method - the tests will fail!

Examples:

twoHighest([1, 2, 10, 8]); // [8, 10]
twoHighest([6, 1, 9, 10, 4]); // [9,10]
twoHighest([4, 25, 3, 20, 19, 5]); // [20,25]
twoHighest([1, 2, 2]) // [2, 2];

minMaxKeyInObject

Write a function called minMaxKeyInObject that accepts an object with numeric keys.*

The function should return an array with the following format: [lowestKey, highestKey]

Examples:

minMaxKeyInObject({ 2: 'a', 7: 'b', 1: 'c', 10: 'd', 4: 'e' });
// [1, 10]
minMaxKeyInObject({ 1: 'Elie', 4: 'Matt', 2: 'Tim' });
// [1, 4]

stringFromObject

Write a function called stringFromObject that generates a string from an object's key/value pairs.

The format should be "key = value, key = value".

Each key/value pair should be separated by a comma and space except for the last pair.

Examples:

stringFromObject({ a: 1, b: '2' });
// "a = 1, b = 2"


stringFromObject({ name: 'Elie', job: 'Instructor', isCatOwner: false });
// "name = Elie, job = Instructor, isCatOwner = false"


stringFromObject({}); // ""

Credit - https://www.codewars.com/kata/building-strings-from-a-hash

countNumbers

Write a function called countNumbers, which accepts an array of strings. The function should return a count of the number of strings in the array that can be successfully converted into a number. For example, the string "1" can be successfully converted to the number 1, but the string "hello" cannot be converted into a number.

Examples:

countNumbers(['a','b','3','awesome','4']); // 2
countNumbers(['32', '55', 'awesome', 'test', '100']); // 3
countNumbers([]); // 0
countNumbers(['4','1','0','NaN']); // 3
countNumbers(['7', '12', 'a', '', '6', '8', ' ']); // 4

removeVowels

Write a function called removeVowels which will accept a string and return a new string with all the vowels removed. You should not consider "y" to be a vowel.

Examples:

removeVowels("Hello!"); // "Hll!"
removeVowels("Tomatoes"); // "Tmts"
removeVowels("Reverse Vowels In The String"); // "Rvrs Vwls n Th Strng"
removeVowels("aeiou"); // ""
removeVowels("why try, shy fly?"); // "why try, shy fly?"

findTheDuplicate

Write a function called findTheDuplicate which accepts an array of numbers containing a single duplicate. The function returns the number which is a duplicate or undefined if there are no duplicates.

Examples:

findTheDuplicate([1,2,1,4,3,12]) // 1
findTheDuplicate([6,1,9,5,3,4,9]) // 9
findTheDuplicate([2,1,3,4]) // undefined

totalCaps

Write a function called totalCaps, which accepts an array of strings and returns the total number of capitals in each of the strings. Do not convert the array into a string.

Examples:

totalCaps(["AwesomE", "ThIngs", "hAppEning", "HerE"]) // 8
totalCaps(["Elie", "Matt", "Tim"]) // 3
totalCaps(["hello", "world"]) // 0

separate

Dogs don't get along with cats, and cats don't get along with dogs.

What they both have in common is that they don't get along with water (baths).

Given an array of 'dogs', 'cats', and 'water', write a function called separate, which returns a new array so that the dogs are separated from the cats by water. Make sure that cats always come first in the array.

You can assume that the array will always at least three elements, and that there'll always be at least one dog, one cat, and one water to work with.

Examples:

separate(['dog','cat','water']) // ['cat','water','dog']

separate(['dog','cat','water','cat']) // ['cat', 'cat', 'water', 'dog'])

separate(['cat','cat','water','dog','water','cat','water','dog'])

// ['cat','cat','cat','water','water','water','dog','dog']

separate(['cat','cat','cat','cat','cat',
    'cat','cat','cat','cat','cat','cat',
    'cat','cat','cat','cat','cat','cat','cat',
    'dog','water','water','water','water','water',
    'water','water','water','water','water','water',
    'water','water','water'])

 /* ['cat','cat','cat','cat','cat',
    'cat','cat','cat','cat','cat','cat',
    'cat','cat','cat','cat','cat','cat','cat',
    'water','water','water','water','water',
    'water','water','water','water','water','water',
    'water','water','water', 'dog']
*/

isAlt

Create a function isAlt that accepts a string as an argument and validates whether the vowels (a, e, i, o, u) and consonants are in alternate order.

Examples:

isAlt("amazon") // true
isAlt("apple") // false
isAlt("banana") // true

Credit - https://www.codewars.com/kata/are-we-alternate