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JavaScript Problem-Solving Questions

JavaScript Problem-Solving Questions

Problem-solving is a critical skill for JavaScript developers. Whether you're preparing for interviews, coding assessments, or real-world projects, tackling JavaScript problems enhances your understanding of the language and your ability to implement effective solutions. This article provides a comprehensive guide to common problem-solving questions in JavaScript, categorized by difficulty level and type.


01. Why Focus on JavaScript Problem-Solving?

JavaScript is a versatile language used for client-side and server-side development. Problem-solving questions are designed to test:

  • Understanding: How well you know JavaScript concepts.
  • Efficiency: Your ability to write optimized code.
  • Creativity: Your approach to solving unique challenges.

02. Beginner-Level Questions

These questions test fundamental JavaScript knowledge.

1. Reverse a String

Problem: Write a function that reverses a string.


// Solution
function reverseString(str) {
  return str.split('').reverse().join('');
}
console.log(reverseString("hello")); // Output: "olleh"

2. Check for Palindromes

Problem: Determine if a string is a palindrome.


// Solution
function isPalindrome(str) {
  const reversed = str.split('').reverse().join('');
  return str === reversed;
}
console.log(isPalindrome("racecar")); // Output: true
console.log(isPalindrome("hello"));   // Output: false

3. Sum of Array Elements

Problem: Calculate the sum of all elements in an array.


// Solution
function sumArray(arr) {
  return arr.reduce((sum, num) => sum + num, 0);
}
console.log(sumArray([1, 2, 3, 4])); // Output: 10

03. Intermediate-Level Questions

These questions test your ability to apply JavaScript concepts to solve more complex problems.

1. Find the Most Frequent Element

Problem: Identify the most frequent element in an array.


// Solution
function mostFrequent(arr) {
  const frequency = {};
  arr.forEach(num => frequency[num] = (frequency[num] || 0) + 1);
  
  let maxCount = 0, mostFrequent;
  for (let key in frequency) {
    if (frequency[key] > maxCount) {
      maxCount = frequency[key];
      mostFrequent = key;
    }
  }
  return mostFrequent;
}
console.log(mostFrequent([1, 3, 2, 3, 2, 3])); // Output: 3

2. Find Prime Numbers in a Range

Problem: Write a function to find all prime numbers in a range.


// Solution
function findPrimes(start, end) {
  const primes = [];
  for (let i = start; i <= end; i++) {
    if (isPrime(i)) primes.push(i);
  }
  return primes;
}

function isPrime(num) {
  if (num < 2) return false;
  for (let i = 2; i <= Math.sqrt(num); i++) {
    if (num % i === 0) return false;
  }
  return true;
}
console.log(findPrimes(10, 20)); // Output: [11, 13, 17, 19]

04. Advanced-Level Questions

These questions challenge your problem-solving and algorithmic thinking.

1. Find the Longest Substring Without Repeating Characters

Problem: Write a function to find the length of the longest substring without repeating characters.


// Solution
function longestUniqueSubstring(str) {
  let maxLength = 0;
  let charSet = new Set();
  let left = 0;
  
  for (let right = 0; right < str.length; right++) {
    while (charSet.has(str[right])) {
      charSet.delete(str[left]);
      left++;
    }
    charSet.add(str[right]);
    maxLength = Math.max(maxLength, right - left + 1);
  }
  return maxLength;
}
console.log(longestUniqueSubstring("abcabcbb")); // Output: 3

2. Merge Overlapping Intervals

Problem: Merge overlapping intervals in an array.


// Solution
function mergeIntervals(intervals) {
  intervals.sort((a, b) => a[0] - b[0]);
  const result = [intervals[0]];
  
  for (let i = 1; i < intervals.length; i++) {
    const last = result[result.length - 1];
    if (intervals[i][0] <= last[1]) {
      last[1] = Math.max(last[1], intervals[i][1]);
    } else {
      result.push(intervals[i]);
    }
  }
  return result;
}
console.log(mergeIntervals([[1, 3], [2, 6], [8, 10], [15, 18]]));
// Output: [[1, 6], [8, 10], [15, 18]]

05. Tips for Solving JavaScript Problems

Effective problem-solving involves understanding the problem and applying the right techniques:

  • Understand the Problem: Break it into smaller parts and ask clarifying questions if necessary.
  • Write Pseudocode: Plan your solution before writing actual code.
  • Optimize: Focus on time and space complexity, especially for larger datasets.
  • Test Your Code: Use different test cases to validate your solution.

06. Resources for Practice


Conclusion

Practicing JavaScript problem-solving questions prepares you for technical interviews and enhances your coding skills. Start with fundamental problems, progress to intermediate and advanced levels, and consistently apply problem-solving strategies. Utilize the provided resources to practice and refine your skills.

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