Level Up Your JavaScript Skills with These 10 Coding Exercises

10 JavaScript Coding Exercises with Explanation and Code

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Ready to sharpen your JavaScript skills? I've put together 10 challenging and rewarding coding exercises that will help you build your confidence and mastery in this essential programming language.

These exercises cover a range of topics, from string manipulation and arrays to functions and calculations. Each exercise includes a clear explanation and helpful tips, so you'll be able to understand the concepts and apply them to your own projects.

Here are just a few of the skills you'll develop:

Reversing strings

Calculating factorials

️ Checking for palindromes

Finding the longest word

Title casing a sentence

Identifying the largest numbers

️♀️ Searching for substrings

Counting character occurrences

Filtering numbers from arrays

Calculating averages

Challenge yourself and take your JavaScript skills to the next level!

1. Reverse a String:

Description: Write a function to reverse a string.

Code:

function reverseString(str) {

  // Using split, reverse, and join methods

  return str.split("").reverse().join("");

}

// Example usage

const str = "Hello world!";

const reversedStr = reverseString(str);

console.log(reversedStr); // !dlrow olleH

2. Factorial of a Number:

Description: Write a function to calculate the factorial of a number.

Code:

function factorial(n) {

  // Base case

  if (n === 0) return 1;

  // Recursive case

  return n * factorial(n - 1);

}

// Example usage

const num = 5;

const factorialResult = factorial(num);

console.log(factorialResult); // 120

3. Check for Palindrome:

Description: Write a function to check if a string is a palindrome (reads the same backwards and forwards).

Code:

function isPalindrome(str) {

  // Convert string to lowercase and remove whitespace

  str = str.toLowerCase().replace(/\s/g, "");

  // Compare string with its reversed version

  return str === str.split("").reverse().join("");

}

// Example usage

const word = "racecar";

const palindromeCheck = isPalindrome(word);

console.log(palindromeCheck); // true

4. Find the Longest Word:

Description: Write a function to find the longest word in a sentence.

Code:

function longestWord(sentence) {

  // Split sentence into words

  const words = sentence.split(" ");

  // Sort words by length (descending)

  words.sort((a, b) => b.length - a.length);

  // Return the first word (longest)

  return words[0];

}

// Example usage

const sentence = "The quick brown fox jumps over the lazy dog.";

const longestWordResult = longestWord(sentence);

console.log(longestWordResult); // jumps

5. Title Case a Sentence:

Description: Write a function to convert a sentence to title case.

Code:

function titleCase(sentence) {

  // Split sentence into words

  const words = sentence.split(" ");

  // For each word, capitalize the first letter and lowercase the rest

  words.forEach((word, index) => {

    words[index] = word.charAt(0).toUpperCase() + word.slice(1).toLowerCase();

  });

  // Join words with spaces

  return words.join(" ");

}

// Example usage

const sentence = "hello world!";

const titleCasedSentence = titleCase(sentence);

console.log(titleCasedSentence); // Hello World!

6. Return Largest Numbers in Arrays:

Description: Write a function to return the largest numbers in an array.

Code:

function largestNumbers(arr) {

  // Use Math.max and spread operator

  return Math.max(...arr);

  // Alternative using loops and conditional statements

  // let largest = arr[0];

  // for (let i = 1; i < arr.length; i++) {

  //   if (arr[i] > largest) largest = arr[i];

  // }

  // return largest;

}

// Example usage

const numbers = [1, 5, 3, 8, 2];

const largestNumber = largestNumbers(numbers);

console.log(largestNumber); // 8

7. Check if a String Contains Another String:

Description: Write a function to check if a string contains another string.

Code:

function containsString(str1, str2) {

  // Use includes method

  return str1.includes(str2);

  // Alternative using indexOf method

  // return str1.indexOf(str2) !== -1;

}

// Example usage

const string1 = "Hello JavaScript";

const string2 = "JavaScript";

const containsCheck = containsString(string1, string2);

console.log(containsCheck); // true

8. Count the Number of Occurrences of a Character:

Description: Write a function to count the number of times a character appears in a string.

Code:

function countChar(str, char) {

  // Use split and filter methods

  return str.split("").filter((c) => c === char).length;

  // Alternative using a loop and counter

  // let count = 0;

  // for (let i = 0; i < str.length; i++) {

  //   if (str[i] === char) count++;

  // }

  // return count;

}

// Example usage

const str = "apple";

const char = "p";

const charCount = countChar(str, char);

console.log(charCount); // 2

9. Filter Numbers from an Array:

Description: Write a function to filter out all non-numeric values from an array.

Code:

function filterNumbers(arr) {

  // Use filter method and isNaN function

  return arr.filter((num) => !isNaN(num));

  // Alternative using a loop and conditional statements

  // const filteredArray = [];

  // for (let i = 0; i < arr.length; i++) {

  //   if (!isNaN(arr[i])) filteredArray.push(arr[i]);

  // }

  // return filteredArray;

}

// Example usage

const mixedArray = ["1", 2, "apple", 3, "banana", 5];

const filteredNumbers = filterNumbers(mixedArray);

console.log(filteredNumbers); // [1, 2, 3, 5]

10. Calculate the Average of an Array:

Description: Write a function to calculate the average of all elements in an array.

Code:

function average(arr) {

  // Use reduce method and length property

  return arr.reduce((acc, num) => acc + num, 0) / arr.length;

}

// Example usage

const numbers = [1, 2, 3, 4, 5];

const averageValue = average(numbers);

console.log(averageValue); // 3

These are just a few examples of simple JavaScript coding exercises. By practicing these and other similar exercises, you can improve your understanding of JavaScript syntax, logic, and problem-solving skills.