Array Method Questions

Given arrays:

const numbers = [5, 12, 8, 130, 44];
const fruits = ["apple", "banana", "cherry", "date", "elderberry"];
const mixedArray = [1, [2, 3], [4, [5, 6]], 7];
const ages = [3, 10, 18, 20, 33];
const colors = ["red", "green", "blue", "yellow"];

Questions

1. Using push()

   • Add "fig" to the end of the fruits array. What does the updated array look like?

2. Using pop()

   • Remove the last item from the fruits array. What item was removed, and what does the array look like now?

3. Using shift() and unshift()

   • Use shift() to remove the first item from the colors array. Then, add "purple" to the start using unshift(). What is the final array?

4. Using map()

   • Create a new array by doubling each value in the numbers array.

5. Using filter()

   • Create a new array from numbers that includes only values greater than 10.

6. Using reduce()

   • Use reduce() on numbers to find the total sum of all elements.

7. Using find()

   • Find the first number in the ages array that is greater than or equal to 18.

8. Using findIndex()

   • Get the index of the first even number in the numbers array.

9. Using includes()

   • Check if "cherry" is present in the fruits array.

10. Using some() and every()

    • Use some() to check if there are any ages greater than 30 in the ages array.
    • Use every() to check if all numbers in the numbers array are positive.

11. Using sort()

    • Sort the colors array alphabetically. Then sort the numbers array in ascending order.

12. Using splice()

    • Remove "banana" and "cherry" from the fruits array using splice().

13. Using concat()

    • Concatenate fruits and colors into a single array. What does the combined array look like?

14. Using slice()

    • Extract the first two elements from colors without modifying the original array.

15. Using flat()

    • Flatten mixedArray into a single-level array.

16. Using forEach()

    • Log each element in the fruits array to the console.

17. Using join()

    • Create a single string from the colors array, with each color separated by a hyphen (-).

#1. Array Of Object

This repository provides practice questions to help users become familiar with JavaScript array methods. The exercises are based on an array of user account objects, each representing a user with properties such as id, name, email, age, balance, and isActive.

Sample Data

Here is the sample data you will use for the exercises:

const users = [
  { id: 1, name: "Alice", email: "alice@example.com", age: 28, balance: 5000, isActive: true },
  { id: 2, name: "Bob", email: "bob@example.com", age: 34, balance: 3000, isActive: false },
  { id: 3, name: "Charlie", email: "charlie@example.com", age: 22, balance: 7000, isActive: true },
  { id: 4, name: "Diana", email: "diana@example.com", age: 29, balance: 4000, isActive: false },
  { id: 5, name: "Eve", email: "eve@example.com", age: 35, balance: 10000, isActive: true },
];

Questions

1. Find all active users:

   • Use the filter method to get a list of users whose isActive property is true.

2. Get the total balance of all users:

   • Use the reduce method to calculate the sum of the balance property for all users.

3. Find a user by email ("charlie@example.com"):

   • Use the find method to locate a user with the email "charlie@example.com".

4. Sort users by age:

   • Use the sort method to order users from youngest to oldest.

5. Increase each user's balance by 10%:

   • Use the map method to create a new array of users with their balance increased by 10%.

6. Check if any user is under 25:

   • Use the some method to check if there is at least one user whose age is less than 25.

7. Check if all users have a balance over 2000:

   • Use the every method to verify if all users have a balance greater than 2000.

8. Get a list of user names:

   • Use the map method to extract just the name property from each user into a new array.

9. Count users with a balance of at least 5000:

   • Use the filter method to find users with a balance of 5000 or more, then get the length of the resulting array.

10. Remove a user by ID (3):

    • Use the filter method to create a new array without the user whose id is 3.

Feel free to modify and extend this README with additional exercises or details as needed. Happy coding!

This version includes only the questions, making it a good starting point for users to practice their skills with JavaScript array methods. Let me know if there's anything else you'd like to add or change!



###2. Array of Objects 

Given the following array:

```javascript
const students = [
  { id: 1, name: "Alice", age: 22, scores: { math: 85, english: 78 } },
  { id: 2, name: "Bob", age: 19, scores: { math: 92, english: 65 } },
  { id: 3, name: "Charlie", age: 23, scores: { math: 88, english: 80 } },
  { id: 4, name: "David", age: 21, scores: { math: 76, english: 95 } },
  { id: 5, name: "Eve", age: 20, scores: { math: 91, english: 83 } }
];

Questions

1. Using map()

   • Create a new array containing only the names of each student.

2. Using filter()

   • Filter out all students who are 21 years old or older.

3. Using reduce()

   • Calculate the total of all math scores.

4. Using find()

   • Find the first student whose English score is above 80.

5. Using some() and every()

   • Check if any student is younger than 20.
   • Verify if every student has scored above 75 in math.

6. Using sort()

   • Sort the students array in ascending order by age.

7. Using forEach()

   • Log a sentence for each student, like "Alice is 22 years old."

---

Challenges

1. Average Math Score Challenge

   • Write a function to find the average math score for all students. What is the result?

2. Top Scorer Challenge

   • Write a function to find the student with the highest math score.

3. English Pass List

   • Create a list of student names who scored 80 or above in English.

4. Age Grouping Challenge

   • Group the students into two categories: those who are under 21 and those who are 21 and older. Return an object with two arrays.

5. Detailed Report Challenge

   • Write a function that returns a report on each student in the format:

     "Alice, age 22, scored 85 in math and 78 in English."

6. Math Improvement Challenge

   • Suppose every student improves their math score by 5 points. Use map() to create a new array reflecting these improved scores.

7. Create a Lookup Table

   • Create an object where each student’s id is a key, and the value is the student’s name. This can be useful for quickly looking up a student’s name by their id.

8. Failed English Challenge

   • Write a function that returns the names of students who scored below 70 in English.

9. Identify Unique Ages

   • Use a combination of methods to find all unique ages in the students array.

10. Score Range Finder

    • Write a function that takes in a score range (e.g., min = 80, max = 90) and returns a list of students whose math scores fall within that range.