14+ Basic JavaScript Programs

14+ Basic Programs Using JavaScript Language

Embark on an exhilarating journey through foundational JavaScript programs! Each program is a stepping stone to mastering coding skills. Feel the thrill as you conquer challenges like removing a class from multiple elements or trimming whitespace from a string. Let your passion drive you through this dynamic language, where every line of code showcases your creativity and determination.

As you tackle each program, enjoy the satisfaction of seeing your ideas come to life—like changing background colors on button click or embedding variables into strings. It’s like riding an emotional rollercoaster through loops, conditionals, and functions. Discover the endless possibilities of JavaScript and let your enthusiasm guide you through the joy of learning and the triumph of overcoming coding obstacles.

1. Reverse a String

Problem: Write a function that reverses a given string.

Example

function reverseString(str) {
  return str.split('').reverse().join('');
}
console.log(reverseString('hello'));

Output:

'olleh'

Explanation

The reverseString function takes a string parameter str. It uses the split('') method to convert the string into an array of characters, reverse() to reverse the array, and join('') to combine the characters back into a string. For example, passing 'hello' results in 'olleh'.

2. Find the Factorial of a Number

Problem: Write a function to calculate the factorial of a given number.

Example

function factorial(num) {
  if (num === 0 || num === 1) {
    return 1;
  }
  return num * factorial(num - 1);
}
console.log(factorial(5));

Output:

Explanation

The factorial function uses recursion to compute the factorial of num. If num is 0 or 1, it returns 1 (base case). Otherwise, it multiplies num by the factorial of num - 1. For num = 5, it calculates 5 * 4 * 3 * 2 * 1 = 120.

3. Check for Palindrome

Problem: Write a function that checks if a given string is a palindrome (reads the same forwards and backwards).

Example

function isPalindrome(str) {
  const reversed = str.split('').reverse().join('');
  return str === reversed;
}
console.log(isPalindrome('racecar'));

Output:

true

Explanation

The isPalindrome function checks if str is a palindrome by comparing it to its reversed version. It creates reversed using split(''), reverse(), and join(''). If str equals reversed, it returns true. For 'racecar', both are identical, so it returns true.

4. Find the Longest Word

Problem: Write a function that finds the longest word in a sentence.

Example

function findLongestWord(sentence) {
  const words = sentence.split(' ');
  let longestWord = '';
  for (const word of words) {
    if (word.length > longestWord.length) {
      longestWord = word;
    }
  }
  return longestWord;
}
console.log(findLongestWord('The quick brown fox'));

Output:

'quick'

Explanation

The findLongestWord function splits sentence into an array of words using split(' '). It initializes longestWord as an empty string and iterates through words. If a word’s length exceeds longestWord’s length, it updates longestWord. For 'The quick brown fox', 'quick' (5 letters) is the longest.

5. Calculate Fibonacci Series

Problem: Write a function to generate the Fibonacci series up to a given number of terms.

Example

function fibonacci(n) {
  const series = [0, 1];
  for (let i = 2; i < n; i++) {
    const next = series[i - 1] + series[i - 2];
    series.push(next);
  }
  return series;
}
console.log(fibonacci(5));

Output:

[0, 1, 1, 2, 3]

Explanation

The fibonacci function generates a Fibonacci series for n terms. It initializes series with [0, 1]. For each index i from 2 to n, it computes next as the sum of the previous two numbers (series[i-1] + series[i-2]) and pushes it to series. For n = 5, it returns [0, 1, 1, 2, 3].

6. Find the Missing Number

Problem: Given an array containing n distinct numbers taken from 0 to n, find the missing number.

Example

function findMissingNumber(nums) {
  const n = nums.length;
  const expectedSum = (n * (n + 1)) / 2;
  const actualSum = nums.reduce((sum, num) => sum + num, 0);
  return expectedSum - actualSum;
}
console.log(findMissingNumber([0, 1, 3]));

Output:

Explanation

The findMissingNumber function finds the missing number in nums. It calculates the expectedSum of numbers from 0 to n using the formula (n * (n + 1)) / 2. The actualSum is computed using reduce. The difference (expectedSum - actualSum) is the missing number. For [0, 1, 3], the missing number is 2.

7. Count the Vowels in a String

Problem: Write a function that counts the number of vowels in a given string.

Example

function countVowels(str) {
  const vowels = 'aeiouAEIOU';
  let count = 0;
  for (const char of str) {
    if (vowels.includes(char)) {
      count++;
    }
  }
  return count;
}
console.log(countVowels('Hello, World!'));

Output:

Explanation

The countVowels function counts vowels in str. It defines vowels as a string of vowels and initializes count to 0. It iterates through each char in str, incrementing count if char is in vowels. For 'Hello, World!', it finds 3 vowels (e, o, o).

8. Check for Anagrams

Problem: Write a function that checks if two strings are anagrams of each other.

Example

function areAnagrams(str1, str2) {
  const sorted1 = str1.split('').sort().join('');
  const sorted2 = str2.split('').sort().join('');
  return sorted1 === sorted2;
}
console.log(areAnagrams('listen', 'silent'));

Output:

true

Explanation

The areAnagrams function checks if str1 and str2 are anagrams. It converts both strings to arrays, sorts them with sort(), and joins them back with join('') to create sorted1 and sorted2. If they’re equal, the strings are anagrams. For 'listen' and 'silent', both sort to 'eilnst', so it returns true.

9. Find the Maximum Number

Problem: Write a function that finds the maximum number in an array of numbers.

Example

function findMax(arr) {
  return Math.max(...arr);
}
console.log(findMax([3, 5, 1, 9, 2]));

Output:

Explanation

The findMax function finds the largest number in arr using Math.max with the spread operator (...) to pass array elements as individual arguments. For [3, 5, 1, 9, 2], it returns 9.

10. Remove Duplicates from an Array

Problem: Write a function that removes duplicate elements from an array.

Example

function removeDuplicates(arr) {
  return Array.from(new Set(arr));
}
console.log(removeDuplicates([1, 2, 2, 3, 4, 4, 5]));

Output:

[1, 2, 3, 4, 5]

Explanation

The removeDuplicates function removes duplicates from arr by converting it to a Set, which automatically removes duplicates, and then back to an array using Array.from. For [1, 2, 2, 3, 4, 4, 5], it returns [1, 2, 3, 4, 5].

11. Calculate the Mean (Average)

Problem: Write a function that calculates the mean (average) of an array of numbers.

Example

function calculateMean(arr) {
  const sum = arr.reduce((acc, num) => acc + num, 0);
  return sum / arr.length;
}
console.log(calculateMean([1, 2, 3, 4, 5]));

Output:

Explanation

The calculateMean function computes the average of arr. It uses reduce to calculate sum by adding all numbers, starting with an accumulator acc of 0. The mean is sum divided by arr.length. For [1, 2, 3, 4, 5], the sum is 15, and the mean is 15 / 5 = 3.

12. Title Case a Sentence

Problem: Write a function that converts the first letter of each word in a sentence to uppercase.

Example

function titleCase(sentence) {
  const words = sentence.split(' ');
  const titleCaseWords = words.map(word => word.charAt(0).toUpperCase() + word.slice(1).toLowerCase());
  return titleCaseWords.join(' ');
}
console.log(titleCase('this is a title'));

Output:

'This Is A Title'

Explanation

The titleCase function capitalizes the first letter of each word in sentence. It splits sentence into words, maps each word by capitalizing its first letter with charAt(0).toUpperCase() and lowercasing the rest with slice(1).toLowerCase(), then joins with join(' '). For 'this is a title', it returns 'This Is A Title'.

13. Check for Prime Number

Problem: Write a function that checks if a given number is prime.

Example

function isPrime(num) {
  if (num <= 1) return false;
  if (num <= 3) return true;
  if (num % 2 === 0 || num % 3 === 0) return false;
  for (let i = 5; i * i <= num; i += 6) {
    if (num % i === 0 || num % (i + 2) === 0) return false;
  }
  return true;
}
console.log(isPrime(7));

Output:

true

Explanation

The isPrime function checks if num is prime. It returns false for num <= 1, true for num <= 3, and false if num is divisible by 2 or 3. It then checks divisibility by numbers of the form 6k ± 1 up to the square root of num. For num = 7, it’s prime, so it returns true.

14. Calculate the Factorial of a Large Number

Problem: Write a function to calculate the factorial of a large number without causing an overflow.

Example

function factorial(num) {
  if (num === 0 || num === 1) return '1';
  let result = BigInt(1);
  for (let i = 2; i <= num; i++) {
    result *= BigInt(i);
  }
  return result.toString();
}
console.log(factorial(100));

Output:

'93326215443944152681699238856266700490715968264381621468592963895217599993229915608941463976156518286253697920827223758251185210916864000000000000000000000000'

Explanation

The factorial function handles large factorials using BigInt to avoid overflow. For num = 0 or 1, it returns '1'. It initializes result as BigInt(1) and multiplies it by BigInt(i) from 2 to num. The result is converted to a string with toString(). For num = 100, it returns a large factorial number.

15. Check if a Number is Even or Odd

Problem: Write a function that checks if a given number is even or odd.

Example

function isEven(num) {
  return num % 2 === 0;
}
console.log(isEven(4)); // true
console.log(isEven(7)); // false

Output:

true
false

Explanation

The isEven function checks if num is even by testing if num % 2 === 0. If true, num is even; otherwise, it’s odd. For num = 4, it returns true; for num = 7, it returns false.

16. Sum of Array Elements

Problem: Write a function that calculates the sum of all elements in an array.

Example

function arraySum(arr) {
  return arr.reduce((sum, num) => sum + num, 0);
}
console.log(arraySum([1, 2, 3, 4]));

Output:

Explanation

The arraySum function computes the sum of arr using reduce, which adds each num to an accumulator sum, starting at 0. For [1, 2, 3, 4], it calculates 1 + 2 + 3 + 4 = 10.

17. Reverse an Array

Problem: Write a function that reverses an array without using the built-in reverse() method.

Example

function reverseArray(arr) {
  const reversed = [];
  for (let i = arr.length - 1; i >= 0; i--) {
    reversed.push(arr[i]);
  }
  return reversed;
}
console.log(reverseArray([1, 2, 3, 4]));

Output:

[4, 3, 2, 1]

Explanation

The reverseArray function reverses arr by creating a new array reversed. It iterates from the last index of arr to the first, pushing each element to reversed. For [1, 2, 3, 4], it returns [4, 3, 2, 1].

These programs and resources are perfect for honing your JavaScript skills. Practice them, experiment, and keep coding!