10 JavaScript Coding Exercises with Explanation and Code
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!
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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.