duracellB/technical-prework-2

JavaScript Prework Problem Set Prework-2

Directions

You will be applying what you've learned about JavaScript by implementing various functions. This assignment will demonstrate your code fluency and problem-solving abilities.

0. Open up this Repl.it in a new tab. Once you open this Repl.it in a new tab, make a personal copy by forking. You should see a blue button in the top right corner that says Fork repl. Click on it!
1. Once the Repl.it has been forked, you will write all your code in the index.js file.
2. The function signatures have already been created for you. You only need to write the body of each function.
3. Do not change the names of the functions. However, you can change the name of the function parameters if you'd like.
4. Each function needs to return a specific value. Make sure none of your functions return undefined.
5. Test your functions by invoking them. You can console.log the invocation of a function to print out its return value. There is a section of code after all functions have been declared where you can test your code.
6. When you are finished, submit the URL of your Repl.it to Canvas.

Coding Problems

1. Write a function that takes an array and returns its first element.

Examples:

firstElement(['hello', 1, true, 6]);  // returns 'hello'
firstElement([2, 3, 'hi']);           // returns 2
firstElement([true, false]);          // returns true

2. Write a function that takes an array and returns its last element.

Examples:

lastElement([2, 3, 'hi']);           // returns 'hi'
lastElement(['hello', 1, true, 6]);  // returns 6
lastElement([true, false]);          // returns false

3. Write a function that takes an array and returns its length.

Examples:

arrayLength([2, 3, 'hi']);           // returns 3
arrayLength(['hello', 1, true, 6]);  // returns 4
arrayLength([true, false]);          // returns 2

4. Write a function that takes an integer argument, and returns an array containing all integers between 1 and the argument (inclusive), in ascending order. You may assume that the argument will always be a positive integer.

Examples:

sequence(5);    // returns [1, 2, 3, 4, 5]
sequence(3);    // returns [1, 2, 3]
sequence(1);    // returns [1]

5. Write a function that takes an array of numbers and returns the sum of all numbers in the original array.

Examples:

sum([6, 7, 8]);         // 21
sum([-100, 2, 1]);      // -97
sum([1.0001, 2, 3]);    // 6.0001

6. Write an average function that takes an array of integers as input, adds all of the integers together, divides the result by the number of entries in the array, and returns the result as a number.

average([1, 2, 6]);     // returns 3 
average([1, 2, 3]);     // returns 2
average([1, 2, 6, 8]);  // returns 4.25
average([-1, 2, 5]);    // returns 2

7. Write a multiplicative average function that takes an array of integers as input, multiplies all of the integers together, divides the result by the number of entries in the array, and returns the result as a number.

multiplicativeAverage([3, 5]);             // returns 7.5
multiplicativeAverage([2, 5, 7, 11, 13]);  // returns 2002

8. Write a function that takes an array of numbers and returns a new array of numbers with the original values negated (make positive numbers negative and make negative numbers positive).

Examples:

negatedArray([3, 6, 8]);          // [-3, -6, -8]
negatedArray([3.25, -2, 5.5]);    // [-3.25, 2, -5.5]
negatedArray([-1, 4, -3]);        // [1, -4, 3]
negatedArray([]);                 // []

9. Write a function that takes an array of numbers and returns a new array of numbers with double the original values.

Examples:

doubleArray([3, 6, 8]);          // [6, 12, 16]
doubleArray([3.25, -2, 5.5]);    // [6.5, -4, 11]
doubleArray([-1, 4, -3]);        // [-2, 8, -6]
doubleArray([]);                 // []

10. Write a function that takes two array arguments, each containing a list of numbers, and returns a new array that contains the sum of each pair of numbers from the arguments that have the same index. You may assume that the arguments contain the same number of elements.

Examples:

addList([3, 5, 7], [9, 10, 11]);         // returns [12, 15, 18]
addList([5, 10, 15, 20], [1, 2, 3, 4]);  // returns [6, 12, 18, 24]

11. Write a function that takes two array arguments, each containing a list of numbers, and returns a new array that contains the product of each pair of numbers from the arguments that have the same index. You may assume that the arguments contain the same number of elements.

Examples:

multiplyList([3, 5, 7], [9, 10, 11]);         // returns [27, 50, 77]
multiplyList([5, 10, 15, 20], [1, 2, 3, 4]);  // returns [5, 20, 45, 80]

12. Write a function that takes in a person object and returns an introduction message. This object argument will have two properties name and age. The returned string should be in the format My name is ... I am ... years old..

Examples:

introducePerson({name: 'Ann', age: 29});    // returns "My name is Ann. I am 29 years old."
introducePerson({age: 30, name: 'Maya'});   // returns "My name is Maya. I am 30 years old."
introducePerson({name: 'Reuben', age: 31}); // returns "My name is Reuben. I am 31 years old."

13. Write a function that determines whether or not someone can vote. The only argument is an object that represents the person. That object has a property age that is a number which represents the person's age in years and a property isCitizen that is true if they are a citizen and false if they are not. The function should return true only if the person is a citizen and is 18 years or older. Otherwise, it should return false.

Examples:

canVote({age: 20, isCitizen: true});     // returns true
canVote({age: 16, isCitizen: true});     // returns false
canVote({isCitizen: false, age: 30});    // returns false
canVote({age: 7, isCitizen: false});     // returns false