Training - Javascript Functions

Fork this repository to your GitHub account, then clone your GitHub copy onto your computer. Write the functions assigned below in the file functions.js. Use snippets to run and observe the results of your code.

Setup

Here's how to use a snippet:

1. Open the Chrome Developer Console (Option + Command + I)
2. Navigate to the Sources tab in the Chrome Developer Console.
3. Click on the Snippets tab within the Sources display.
4. Right-click and choose New to create a new Snippets file.
5. Name the Snippets File myFunctions.
6. Write or paste code into the editing window and press cmd + return to run the code.

You'll be filling in a bunch of empty function definitions. Type each blank function definition into the snippet, then you write the rest of the code to make the function work.

After you implement a function successfully in your snippet, copy it over into the functions.js file. Unless a different behavior is specified, have the function log the answer to the console AND return it.

Notice there is a solutions.js file. Make a full attempt at finishing these on your own and refer to the solutions only when you are finished or unbearably stuck. Also recognize that the solutions are only one solution and that there are many good ways to solve these problems.

For some of the problems, you'll have to use functions or other variables supplied by JavaScript's built-in Math object. Here is the documentation on using the Math object.

Example Usage of Math

	var absoluteValue = Math.abs(-4);
	// evaluates to 4

	var fourSquared = Math.pow(4, 2);
	// evaluates to 16

	var roundedToNearestInteger = Math.round(1.22343);
	// evaluates to 1

Function Definitions!

1. Build your own concatenation

Return a new string that is the combination of two arguments passed into the function

Example: dog and house will return doghouse

Function signature (only look at this after you've thought about what it should look like)

function combineWords(word1, word2) {
	// TODO: Place your code here
}
var result = combineWords('dog', 'house');
console.log(result);
// displays 'doghouse'

2. Repeat a phrase

Display an argument phrase to the console n times

Function signature (only look at this after you've thought about what it should look like)

function repeatPhrase(phrase, n) {
	// TODO: Place your code here
}

repeatPhrase("Hello", 5);
// displays
// Hello
// Hello
// Hello
// Hello
// Hello

3. Build your own Power function

Return number ^power without using built-in Math functions.

Example:
4⁵ = 4 * 4 * 4 * 4 * 4 = 1024

Function signature (only look at this after you've thought about what it should look like)

function toTheNthPower(number, power) {
	// TODO: Place your code here		
}

var result = toTheNthPower(4, 5);
console.log(result);
// displays 1024

4. Area of a circle: π r²

Return the area of a circle given the radius
background information

Function signature (only look at this after you've thought about what it should look like)

function areaOfACircle(radius) {
	// TODO: Place your code here
}

var result = areaOfACircle(2);
console.log(result);
// displays approximately 12.57

5. Pythagorean Theorem: a² + b² = c²

Return c given a and b. background information

Function signature (only look at this after you've thought about what it should look like)

function pythagoreanTheorem(a, b) {
	// TODO: Place your code here
}

var result = pythagoreanTheorem(3, 4);
console.log(result);
// should display 5;

6. Is X Evenly Divisible by Y ?

Return a boolean value whether or not X can be divided by Y without any remainders.

Hint: Explore the world of Modulus operators!

Function signature (only look at this after you've thought about what it should look like)

function isXEvenlyDivisibleByY(x, y) {
	// TODO: Place your code here
}

var result = isXEvenlyDivisibleByY(99, 3);
console.log(result);
// displays true

7. Vowel Count:

Return the number of occurrences of vowels in a word. Vowels are a, e, i, o, u, and y

Function signature (only look at this after you've thought about what it should look like)

function countVowels(word) {
	// TODO: Place your code here
}

var result = countVowels("stealing");
console.log(result);
// displays 3

Challenge: Can you alter the code to count both upper case AND lower case?

8. Does the array contain "wdi"?

Given an array, return true if it contains the string "wdi" and false if it does not contain that string.

findWdi([9,'Bart Simpson', true, 'wdi']) // returns true
findWdi(['a','b','c']) // returns false

Function signature (only look at this after you've thought about what it should look like)

	function findWdi(arr){
		// TODO: Place your code here
	}

9. Find the longest word in a sentence

Given a string representing a sentence, return the longest word in that sentence.

Function signature (only look at this after you've thought about what it should look like)

findLongestWord("The rain in Spain falls mainly on the plain"); // => "mainly"
findLongestWord("abcdefghijkl"); // => "abcdefghijkl"

function findLongestWord(sentence) {
    // TODO: Place your code here
}

10. Build an ASCII Triangle!

Display a simple triangle with asterisks

Example:
printTriangle(5)

*
**
***
****
*****

Function signature (only look at this after you've thought about what it should look like)

function printTriangle(length) {
	// TODO: Place your code here
}

printTriangle(3);
// displays
// *
// **
// ***

11. Create a heads-or-tails game.

In a separate file, create a super-simple HTML page that contains an element with the id result, and link your HTML page to a js file. In that js file, define 3 functions:

• A function that returns either "heads" or "tails", the result of a coin flip.
• A function that, when called, prompts the user to guess either "heads" or "tails" and returns their guess.
• A function that takes in a string and puts that string into the result element on your page.

Then, write a fourth function that wraps all of these functions into one, so that calling that fourth function will prompt the user to guess heads or tails, flip a coin, and then tell the user whether or not they were right. Make sure that calling just that function from the console works as expected.

12. Stretch Challenge: Can you alter the printTriangle function to create a Pyramid?

Example: printPyramid(10);

           *
          * *
         * * *
        * * * *
       * * * * *
      * * * * * *
     * * * * * * *
    * * * * * * * *
   * * * * * * * * *
  * * * * * * * * * *

Warning: This is a surprisingly tricky interview-level exercise. Try at your own risk!

function printPyramid(length) {
	// TODO: Place your code here
}