If you're looking to practice your JavaScript skills, array manipulation is a great place to start. Here are challenges that will help you hone your skills.

1. Unique Strings
Write a function that takes an array of strings and returns a new array with only the unique strings.

Solution: uniqueStrings.js

2. Objects with Certain Properties
Write a function that takes an array of objects and returns a new array with only the objects that have a certain property.

Solution: objectsWithCertainProperties.js

3. Sorted Numbers
Write a function that takes an array of numbers and returns a new array with the numbers sorted in descending order.

Solution: sortedNumbersDescending.js

Write a function that takes an array of numbers and returns a new array with all the numbers sorted in ascending order.

Solution: sortedNumbersAscending.js

4. Sum and Average
Write a function that takes an array of numbers and returns the sum of all the numbers.

Solution: sumOfNumbers.js

Write a function that takes an array of numbers and returns the average of all the numbers.

Solution: averageOfNumbers.js

5. Longest and Shortest Strings
Write a function that takes an array of strings and returns the longest string in the array.

Solution: longestString.js

Write a function that takes an array of strings and returns the shortest string in the array.

Solution: shortestString.js

6. Largest and Smallest Numbers
Write a function that takes an array of numbers and returns the largest number in the array.

Solution: largestNumber.js

Write a function that takes an array of numbers and returns the smallest number in the array.

Solution: smallestNumber.js

7. Even and Odd Numbers
Write a function that takes an array of numbers and returns a new array with only the even numbers.

Solution: evenNumbers.js

Write a function that takes an array of numbers and returns a new array with only the odd numbers.

Solution: oddNumbers.js

8. Values of a Key in an Array of Objects
Write a function that takes an array of objects and a key, and returns a new array with the values of the specified key in each object.

Solution: valuesOfKey.js

I hope these challenges help you improve your JavaScript skills. If you have any questions or feedback, feel free to leave a comment or reach out to me on GitHub. Happy coding!